'' (or <section>) tag rather than the header itself. This allows entire sections to be manipulated using javascript or treated differently in CSS.

Pandoc Extension: ''implicit_header_references'' ####

Pandoc behaves as if reference links have been defined for each header. So, to link to a header

  # Header identifiers in HTML

you can simply write

  [Header identifiers in HTML]

or

  [Header identifiers in HTML][]

or

  [the section on header identifiers][header identifiers in
  HTML]

instead of giving the identifier explicitly:

  [[#header-identifiers-in-html|Header identifiers in HTML]]

If there are multiple headers with identical text, the corresponding reference will link to the first one only, and you will need to use explicit links to link to the others, as described above.

Like regular reference links, these references are case-insensitive.

Explicit link reference definitions always take priority over implicit header references. So, in the following example, the link will point to bar, not to #foo:

  # Foo

  [foo]: bar

  See [foo]

Pandoc Extension: ''blank_before_blockquote'' ####

Standard Markdown syntax does not require a blank line before a block quote. Pandoc does require this (except, of course, at the beginning of the document). The reason for the requirement is that it is all too easy for a > to end up at the beginning of a line by accident (perhaps through line wrapping). So, unless the markdown_strict format is used, the following does not produce a nested block quote in pandoc:

  > This is a block quote.
  >> Nested.

Pandoc Extension: ''fenced_code_blocks'' ####

In addition to standard indented code blocks, pandoc supports *fenced* code blocks. These begin with a row of three or more tildes (~) and end with a row of tildes that must be at least as long as the starting row. Everything between these lines is treated as code. No indentation is necessary:

  ~~~~~~~
  if (a > 3) {
    moveShip(5 * gravity, DOWN);
  }
  ~~~~~~~

Like regular code blocks, fenced code blocks must be separated from surrounding text by blank lines.

If the code itself contains a row of tildes or backticks, just use a longer row of tildes or backticks at the start and end:

  ~~~~~~~~~~~~~~~~
  ~~~~~~~~~~
  code including tildes
  ~~~~~~~~~~
  ~~~~~~~~~~~~~~~~

Pandoc Extension: ''backtick_code_blocks'' ####

Same as fenced_code_blocks, but uses backticks (`'' '' ``) instead of tildes (~).

Pandoc Extension: ''fenced_code_attributes'' ####

Optionally, you may attach attributes to fenced or backtick code block using this syntax:

  ~~~~ {#mycode .haskell .numberLines startFrom="100"}
  qsort []     = []
  qsort (x:xs) = qsort (filter (< x) xs) ++ [x] ++
                 qsort (filter (>= x) xs)
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here mycode is an identifier, haskell and numberLines are classes, and startFrom is an attribute with val.. .ue 100. Some output formats can use this information to do syntax highlighting. Currently, the only output formats that uses this information are HTML and LaTeX. If highlighting is supported for your output format and language, then the code block above will appear highlighted, with numbered lines. (To see which languages are supported, do pandoc –version.) Otherwise, the code block above will appear as follows:

  <pre id="mycode" class="haskell numberLines" startFrom="100">
    <code>
    ...
    </code>
  </pre>

A shortcut form can also be used for specifying the language of the code block:

    qsort [] = []

This is equivalent to:

    qsort [] = []

If the fenced_code_attributes extension is disabled, but input contains class attribute(s) for the codeblock, the first class attribute will be printed after the opening fence as a bare word.

To prevent all highlighting, use the –no-highlight flag. To set the highlighting style, use –highlight-style. For more information on highlighting, see [Syntax highlighting], below.

Pandoc Extension: ''line_blocks'' ####

A line block is a sequence of lines beginning with a vertical bar (|) followed by a space. The division into lines will be preserved in the output, as will any leading spaces; otherwise, the lines will be formatted as Markdown. This is useful for verse and addresses:

  | The limerick packs laughs anatomical
  | In space that is quite economical.
  |    But the good ones I've seen
  |    So seldom are clean
  | And the clean ones so seldom are comical

  | 200 Main St.
  | Berkeley, CA 94718

The lines can be hard-wrapped if needed, but the continuation line must begin with a space.

  | The Right Honorable Most Venerable and Righteous Samuel L.
    Constable, Jr.
  | 200 Main St.
  | Berkeley, CA 94718

This syntax is borrowed from [reStructuredText].

Pandoc Extension: ''fancy_lists'' ####

Unlike standard Markdown, pandoc allows ordered list items to be marked with uppercase and lowercase letters and roman numerals, in addition to arabic numerals. List markers may be enclosed in parentheses or followed by a single right-parentheses or period. They must be separated from the text that follows by at least one space, and, if the list marker is a capital letter with a period, by at least two spaces.[^2]

[^2]: The point of this rule is to ensure that normal paragraphs

  starting with people's initials, like

      B. Russell was an English philosopher.

  do not get treated as list items.

  This rule will not prevent

      (C) 2007 Joe Smith

  from being interpreted as a list item.  In this case, a backslash
  escape can be used:

      (C\) 2007 Joe Smith

The fancy_lists extension also allows '#' to be used as an ordered list marker in place of a numeral:

  #. one
  #. two

Pandoc Extension: ''startnum'' ####

Pandoc also pays attention to the type of list marker used, and to the starting number, and both of these are preserved where possible in the output format. Thus, the following yields a list with numbers followed by a single parenthesis, starting with 9, and a sublist with lowercase roman numerals:

   9)  Ninth
  10)  Tenth
  11)  Eleventh
         i. subone
        ii. subtwo
       iii. subthree

Pandoc will start a new list each time a different type of list marker is used. So, the following will create three lists:

  (2) Two
  (5) Three
    - Four
  *   Five

If default list markers are desired, use #.:

  #.  one
  #.  two
  #.  three

Pandoc Extension: ''definition_lists'' ####

Pandoc supports definition lists, using the syntax of [PHP Markdown Extra] with some extensions.[^3]

  Term 1

  :   Definition 1

  Term 2 with *inline markup*

  :   Definition 2

          { some code, part of Definition 2 }

      Third paragraph of definition 2.

Each term must fit on one line, which may optionally be followed by a blank line, and must be followed by one or more definitions. A definition begins with a colon or tilde, which may be indented one or two spaces.

A term may have multiple definitions, and each definition may consist of one or more block elements (paragraph, code block, list, etc.), each indented four spaces or one tab stop. The body of the definition (including the first line, aside from the colon or tilde) should be indented four spaces. However, as with other Markdown lists, you can “lazily” omit indentation except at the beginning of a paragraph or other block element:

  Term 1

  :   Definition
  with lazy continuation.

      Second paragraph of the definition.

If you leave space before the definition (as in the example above), the text of the definition will be treated as a paragraph. In some output formats, this will mean greater spacing between term/definition pairs. For a more compact definition list, omit the space before the definition:

  Term 1
    ~ Definition 1

  Term 2
    ~ Definition 2a
    ~ Definition 2b

Note that space between items in a definition list is required……… (A variant that loosens this requirement, but disallows “lazy” hard wrapping, can be activated with compact_definition_lists: see [Non-pandoc extensions], below.)

[^3]: I have been influenced by the suggestions of David Wheeler.

Pandoc Extension: ''example_lists'' ####

The special list marker @ can be used for sequentially numbered examples. The first list item with a @ marker will be numbered '1', the next '2', and so on, throughout the document. The numbered examples need not occur in a single list; each new list using @ will take up where the last stopped. So, for example:

  (@)  My first example will be numbered (1).
  (@)  My second example will be numbered (2).

  Explanation of examples.

  (@)  My third example will be numbered (3).

Numbered examples can be labeled and referred to elsewhere in the document:

  (@good)  This is a good example.

  As (@good) illustrates, ...

The label can be any string of alphanumeric characters, underscores, or hyphens.

Compact and loose lists ###

Pandoc behaves differently from Markdown.pl on some “edge cases” involving lists. Consider this source:

  +   First
  +   Second:
  	-   Fee
  	-   Fie
  	-   Foe

  +   Third

Pandoc transforms this into a “compact list” (with no <p> tags around “First”, “Second”, or “Third”), while Markdown puts <p> tags around “Second” and “Third” (but not “First”), because of the blank space around “Third”. Pandoc follows a simple rule: if the text is followed by a blank line, it is treated as a paragraph. Since “Second” is followed by a list, and not a blank line, it isn't treated as a paragraph. The fact that the list is followed by a blank line is irrelevant. (Note: Pandoc works this way even when the markdown_strict format is specified. This behavior is consistent with the official Markdown syntax description, even though it is different from that of Markdown.pl.)

Ending a list ###

What if you want to put an indented code block after a list?

1. item one
2. item two

      { my code block }

Trouble! Here pandoc (like other Markdown implementations) will treat { my code block } as the second paragraph of item two, and not as a code block.

To “cut off” the list after item two, you can insert some non-indented content, like an HTML comment, which won't produce visible output in any format:

1. item one
2. item two

  <!-- end of list -->

      { my code block }

You can use the same trick if you want two consecutive lists instead of one big list:

1. one
2. two
3. three

  <!-- -->

1. uno
2. dos
3. tres

Pandoc Extension: ''table_captions'' ####

A caption may optionally be provided with all 4 kinds of tables (as illustrated in the examples below). A caption is a paragraph beginning with the string Table: (or just :), which will be stripped off. It may appear either before or after the table.

Pandoc Extension: ''simple_tables'' ####

Simple tables look like this:

    Right     Left     Center     Default
  -------     ------ ----------   -------
       12     12        12            12
      123     123       123          123
        1     1          1             1

  Table:  Demonstration of simple table syntax.

The headers and table rows must each fit on one line. Column alignments are determined by the position of the header text relative to the dashed line below it:[^4]

• If the dashed line is flush with the header text on the right side but extends beyond it on the left, the column is right-aligned.
• If the dashed line is flush with the header text on the left side but extends beyond it on the right, the column is left-aligned.
• If the dashed line extends beyond the header text on both sides, the column is centered.
• If the dashed line is flush with the header text on both sides, the default alignment is used (in most cases, this will be left).

[^4]: This scheme is due to Michel Fortin, who proposed it on the

     [[http://six.pairlist.net/pipermail/markdown-discuss/2005-March/001097.html|Markdown discussion list]].

The table must end with a blank line, or a line of dashes followed by a blank line.

The column headers may be omitted, provided a dashed line is used to end the table. For example:

1. —— —— ———- ——-

12 12 12 12

      123     123       123           123
        1     1          1              1
  -------     ------ ----------   -------

1. —— —— ———- ——-

12 12 12 12

  123     123       123           123
    1     1          1              1
  -------     ------ ----------   -------

When headers are omitted, column alignments are determined on the basis of the first line of the table body. So, in the tables above, the columns would be right, left, center, and right aligned, respectively.

Pandoc Extension: ''multiline_tables'' ####

Multiline tables allow headers and table rows to span multiple lines of text (but cells that span multiple columns or rows of the table are not supported). Here is an example:

   Centered   Default           Right Left
    Header    Aligned         Aligned Aligned
  ----------- ------- --------------- -------------------------
     First    row                12.0 Example of a row that
                                      spans multiple lines.

    Second    row                 5.0 Here's another one. Note
                                      the blank line between
                                      rows.

  Table: Here's the caption. It, too, may span
  multiple lines.

These work like simple tables, but with the following differences:

• They must begin with a row of dashes, before the header text

(unless the headers are omitted).

• They must end with a row of dashes, then a blank line.
• The rows must be separated by blank lines.

In multiline tables, the table parser pays attention to the widths of the columns, and the writers try to reproduce these relative widths in the output. So, if you find that one of the columns is too narrow in the output, try widening it in the Markdown source.

Headers may be omitted in multiline tables as well as simple tables:

1. ———- ——- ————— ————————- First row 12.0 Example of a row that

spans multiple lines.

    Second    row                 5.0 Here's another one. Note
                                      the blank line between
                                      rows.
  ----------- ------- --------------- -------------------------

  : Here's a multiline table without headers.
  
  ---------- ------- --------------- -------------------------
  First    row                12.0 Example of a row that
                                  spans multiple lines.

  Second    row                 5.0 Here's another one. Note
                                  the blank line between
                                  rows.
  ---------- ------- --------------- -------------------------

: Here's a multiline table without headers.

It is possible for a multiline table to have just one row, but the row should be followed by a blank line (and then the row of dashes that ends the table), or the table may be interpreted as a simple table.

Pandoc Extension: ''grid_tables'' ####

Grid tables look like this:

  : Sample grid table.

  +---------------+---------------+--------------------+
  | Fruit         | Price         | Advantages         |
  +===============+===============+====================+
  | Bananas       | $1.34         | - built-in wrapper |
  |               |               | - bright color     |
  +---------------+---------------+--------------------+
  | Oranges       | $2.10         | - cures scurvy     |
  |               |               | - tasty            |
  +---------------+---------------+--------------------+

: Sample grid table.

+—————+—————+——————–+

+===============+===============+====================+

+—————+—————+——————–+

+—————+—————+——————–+

The row of =s separates the header from the table body, and can be omitted for a headerl. …….ess table. The cells of grid tables may contain arbitrary block elements (multiple paragraphs, code blocks, lists, etc.). Alignments are not supported, nor are cells that span multiple columns or rows. Grid tables can be created easily using [Emacs table mode].

[Emacs table mode]: http://table.sourceforge.net/

Pandoc Extension: ''pipe_tables'' ####

Pipe tables look like this:

  | Right | Left | Default | Center |
  |------:|:-----|---------|:------:|
  |   12  |  12  |    12   |    12  |
  |  123  |  123 |   123   |   123  |
  |    1  |    1 |     1   |     1  |

    : Demonstration of pipe table syntax.

  : Demonstration of pipe table syntax.

The syntax is identical to [PHP Markdown Extra tables]. The beginning and ending pipe characters are optional, but pipes are required between all columns. The colons indicate column alignment as shown. The header cannot be omitted. To simulate a headerless table, include a header with blank cells.

Since the pipes indicate column boundaries, columns need not be vertically aligned, as they are in the above example. So, this is a perfectly legal (though ugly) pipe table:

  fruit| price
  -----|-----:
  apple|2.05
  pear|1.37
  orange|3.09

The cells of pipe tables cannot contain block elements like paragraphs and lists, and cannot span multiple lines. If a pipe table contains a row whose printable content is wider than the column width (see –columns), then the cell contents will wrap, with the relative cell widths determined by the widths of the separator lines.

Note: pandoc also recognizes pipe tables of the following form, as can be produced by Emacs' orgtbl-mode:

  | One | Two   |
  |-----+-------|
  | my  | table |
  | is  | nice  |

The difference is that + is used instead of |. Other orgtbl features are not supported. In particular, to get non-default column alignment, you'll need to add colons as above.

[PHP Markdown Extra tables]: https://michelf.ca/projects/php-markdown/extra/#table

Pandoc Extension: ''pandoc_title_block'' ####

If the file begins with a title block

  % title
  % author(s) (separated by semicolons)
  % date

it will be parsed as bibliographic information, not regular text. (It will be used, for example, in the title of standalone LaTeX or HTML output.) The block may contain just a title, a title and an author, or all three elements. If you want to include an author but no title, or a title and a date but no author, you need a blank line:

  %
  % Author

  % My title
  %
  % June 15, 2006

The title may occupy multiple lines, but continuation lines must begin with leading space, thus:

  % My title
    on multiple lines

If a document has multiple authors, the authors may be put on separate lines with leading space, or separated by semicolons, or both. So, all of the following are equivalent:

  % Author One
    Author Two

  % Author One; Author Two

  % Author One;
    Author Two

The date must fit on one line.

All three metadata fields may contain standard inline formatting (italics, links, footnotes, etc.).

Title blocks will always be parsed, but they will affect the output only when the –standalone (-s) option is chosen. In HTML output, titles will appear twice: once in the document head – this is the title that will appear at the top of the window in a browser – and once at the beginning of the document body. The title in the document head can have an optional prefix attached (–title-prefix or -T option). The title in the body appears as an H1 element with class “title”, so it can be suppressed or reformatted with CSS. If a title prefix is specified with -T and no title block appears in the document, the title prefix will be used by itself as the HTML title.

The man page writer extracts a title, man page section number, and other header and footer information from the title line. The title is assumed to be the first word on the title line, which may optionally end with a (single-digit) section number in parentheses. (There should be no space between the title and the parentheses.) Anything after this is assumed to be additional footer and header text. A single pipe character (|) should be used to separate the footer text from the header text. Thus,

  % PANDOC(1)

will yield a man page with the title PANDOC and section 1.

  % PANDOC(1) Pandoc User Manuals

will also have “Pandoc User Manuals” in the footer.

  % PANDOC(1) Pandoc User Manuals | Version 4.0

will also have “Version 4.0” in the header.

Pandoc Extension: ''yaml_metadata_block'' ####

A YAML metadata block is a valid YAML object, delimited by a line of three hyphens (—) at the top and a line of three hyphens (—) or three dots (…) at the bottom. A YAML metadata block may occur anywhere in the document, but if it is not at the beginning, it must be preceded by a blank line. (Note that, because of the way pandoc concatenates input files when several are provided, you may also keep the metadata in a separate YAML file and pass it to pandoc as an argument, along with your Markdown files:

  pandoc chap1.md chap2.md chap3.md metadata.yaml -s -o book.html

Just be sure that the YAML file begins with — and ends with — or ….)

Metadata will be taken from the fields of the YAML object and added to any existing document metadata. Metadata can contain lists and objects (nested arbitrarily), but all string scalars will be interpreted as Markdown. Fields with names ending in an underscore will be ignored by pandoc. (They may be given a role by external processors.)

A document may contain multiple metadata blocks. The metadata fields will be combined through a *left-biased union*: if two metadata blocks attempt to set the same field, the value from the first block will be taken.

When pandoc is used with -t markdown to create a Markdown document, a YAML metadata block will be produced only if the -s/–standalone option is used. All of the metadata will appear in a single block at the beginning of the document.

Note that YAML escaping rules must be followed. Thus, for example, if a title contains a colon, it must be quoted. The pipe character (|) can be used to begin an indented block that will be interpreted literally, without need for escaping. This form is necessary when the field contains blank lines:

1. -

title: 'This is the title: it contains a colon'

  author:
  - name: Author One
    affiliation: University of Somewhere
  - name: Author Two
    affiliation: University of Nowhere
  tags: [nothing, nothingness]
  abstract: |
    This is the abstract.

    It consists of two paragraphs.
  ...

Template variables will be set automatically from the metadata. Thus, for example, in writing HTML, the variable abstract will be set to the HTML equivalent of the Markdown in the abstract field:

  <p>This is the abstract.</p>
  <p>It consists of two paragraphs.</p>

Note: The author variable in the default templates expects a simple list or string. To use the structured authors in the example, you would need a custom template. For example:

  $for(author)$
  $if(author.name)$
  $author.name$$if(author.affiliation)$ ($author.affiliation$)$endif$
  $else$
  $author$
  $endif$
  $endfor$

Pandoc Extension: ''all_symbols_escapable'' ####

Except inside a code block or inline code, any punctuation or space character preceded by a backslash will be treated literally, even if it would normally indicate formatting. Thus, for example, if one writes

• \*hello\**

one will get

  <em>*hello*</em>

instead of

  <strong>hello</strong>

This rule is easier to remember than standard Markdown's rule, which allows only the following characters to be backslash-escaped:

  \`*_{}[]()>#+-.!

(However, if the markdown_strict format is used, the standard Markdown rule will be used.)

A backslash-escaped space is parsed as a nonbreaking space. It will appear in TeX output as ~ and in HTML and XML as \  or \ .

A backslash-escaped newline (i.e. a backslash occurring at the end of a line) i… …..s parsed as a hard line break. It will appear in TeX output as \\ and in HTML as <br />. This is a nice alternative to Markdown's “invisible” way of indicating hard line breaks using two trailing spaces on a line.

Backslash escapes do not work in verbatim contexts.

Pandoc Extension ####

If the –smart option is specified, pandoc will produce typographically correct output, converting straight quotes to curly quotes, — to em-dashes, – to en-dashes, and … to ellipses. Nonbreaking spaces are inserted after certain abbreviations, such as “Mr.”

Note: if your LaTeX template or any included header file call for the [csquotes] package, pandoc will detect this automatically and use \enquote{…} for quoted text.

Pandoc Extension: ''intraword_underscores'' ####

Because _ is sometimes used inside words and identifiers, pandoc does not interpret a _ surrounded by alphanumeric characters as an emphasis marker. If you want to emphasize just part of a word, use *:

  feas*ible*, not feas*able*.

Pandoc Extension: ''strikeout'' ####

To strikeout a section of text with a horizontal line, begin and end it with ~~. Thus, for example,

  This ~~is deleted text.~~

Pandoc Extension: ''superscript'', ''subscript'' ####

Superscripts may be written by surrounding the superscripted text by ^ characters; subscripts may be written by surrounding the subscripted text by ~ characters. Thus, for example,

  H~2~O is a liquid.  2^10^ is 1024.

If the superscripted or subscripted text contains spaces, these spaces must be escaped with backslashes. (This is to prevent accidental superscripting and subscripting through the ordinary use of ~ and ^.) Thus, if you want the letter P with 'a cat' in subscripts, use P~a\ cat~, not P~a cat~.

Pandoc Extension: ''inline_code_attributes'' ####

Attributes can be attached to verbatim text, just as with [fenced code blocks]:

  ''<$>''{.haskell}

Small caps ###

To write small caps, you can use an HTML span tag:

  <span style="font-variant:small-caps;">Small caps</span>

(The semicolon is optional and there may be space after the colon.) This will work in all output formats that support small caps.

Pandoc Extension: ''raw_html'' ####

Markdown allows you to insert raw HTML (or DocBook) anywhere in a document (except verbatim contexts, where <, >, and & are interpreted literally). (Technically this is not an extension, since standard Markdown allows it, but it has been made an extension so that it can be disabled if desired.)

The raw HTML is passed through….. … unchanged in HTML, S5, Slidy, Slideous, DZSlides, EPUB, Markdown, and Textile output, and suppressed in other formats.

Pandoc Extension: ''markdown_in_html_blocks'' ####

Standard Markdown allows you to include HTML “blocks”: blocks of HTML between balanced tags that are separated from the surrounding text with blank lines, and start and end at the left margin. Within these blocks, everything is interpreted as HTML, not Markdown; so (for example), * does not signify emphasis.

Pandoc behaves this way when the markdown_strict format is used; but by default, pandoc interprets material between HTML block tags as Markdown. Thus, for example, pandoc will turn

  <table>
  <tr>
  <td>*one*</td>
  <td>[[http://google.com|a link]]</td>
  </tr>
  </table>

into

  <table>
  <tr>
  <td><em>one</em></td>
  <td><a href="http://google.com">a link</a></td>
  </tr>
  </table>

whereas Markdown.pl will preserve it as is.

There is one exception to this rule: text between <script> and <style> tags is not interpreted as Markdown.

This departure from standard Markdown should make it easier to mix Markdown with HTML block elements. For example, one can surround a block of Markdown text with

  # References {.allowframebreaks}

  <div class="notes">
  This is my note.

  </div>

  # Fragile slide {.fragile}

  creator:
  - role: author
    text: John Smith
  - role: editor
    text: Sarah Jones
  identifier:
  - scheme: DOI
    text: doi:10.234234.234/33
  publisher:  My Press
  rights: © 2007 John Smith, CC BY-NC
  ...

~ Either a string value or an object with fields ''text'' and
  ''scheme''.  Valid values for ''scheme'' are ''ISBN-10'',
  ''GTIN-13'', ''UPC'', ''ISMN-10'', ''DOI'', ''LCCN'', ''GTIN-14'',
  ''ISBN-13'', ''Legal deposit number'', ''URN'', ''OCLC'',
  ''ISMN-13'', ''ISBN-A'', ''JP'', ''OLCC''.

~ Either a string value, or an object with fields ''file-as'' and
  ''type'', or a list of such objects.  Valid values for ''type'' are
  ''main'', ''subtitle'', ''short'', ''collection'', ''edition'', ''extended''.

~ Either a string value, or an object with fields ''role'', ''file-as'',
  and ''text'', or a list of such objects.  Valid values for ''role'' are
  [MARC relators], but
  pandoc will attempt to translate the human-readable versions
  (like "author" and "editor") to the appropriate marc relators.

~ Same format as ''creator''.

~ A string value in ''YYYY-MM-DD'' format.  (Only the year is necessary.)
  Pandoc will attempt to convert other common date formats.

~ A string value in [BCP 47] format.  Pandoc will default to the local
  language if nothing is specified.

~ A string value or a list of such values.

~ A string value.

~ A string value.

~ A string value.

~ A string value.

~ A string value.

~ A string value.

~ A string value (path to cover image).

~ A string value (path to CSS stylesheet).

~ Either ''ltr'' or ''rtl''. Specifies the ''page-progression-direction''
  attribute for the [''spine'' element].

  <audio controls="1">
    <source src="http://example.com/music/toccata.mp3"
            data-external="1" type="audio/mpeg">
    </source>
  </audio>