Updated spec.txt.

Author: jgm

test/spec.txt

@@ -11,10 +11,12 @@ license: '[CC-BY-SA 4.0](http://creativecommons.org/licenses/by-sa/4.0/)'
 ## What is Markdown?
 
 Markdown is a plain text format for writing structured documents,
-based on conventions used for indicating formatting in email and
-usenet posts.  It was developed in 2004 by John Gruber, who wrote
-the first Markdown-to-HTML converter in Perl, and it soon became
-ubiquitous.  In the next decade, dozens of implementations were
+based on conventions for indicating formatting in email
+and usenet posts.  It was developed by John Gruber (with
+help from Aaron Swartz) and released in 2004 in the form of a
+[syntax description](http://daringfireball.net/projects/markdown/syntax)
+and a Perl script (`Markdown.pl`) for converting Markdown to
+HTML.  In the next decade, dozens of implementations were
 developed in many languages.  Some extended the original
 Markdown syntax with conventions for footnotes, tables, and
 other document elements.  Some allowed Markdown documents to be
@@ -312,7 +314,7 @@ form feed (`U+000C`), or carriage return (`U+000D`).
 characters].
 
 A [Unicode whitespace character](@) is
-any code point in the Unicode `Zs` class, or a tab (`U+0009`),
+any code point in the Unicode `Zs` general category, or a tab (`U+0009`),
 carriage return (`U+000D`), newline (`U+000A`), or form feed
 (`U+000C`).
 
@@ -331,7 +333,7 @@ is `!`, `"`, `#`, `$`, `%`, `&`, `'`, `(`, `)`,
 
 A [punctuation character](@) is an [ASCII
 punctuation character] or anything in
-the Unicode classes `Pc`, `Pd`, `Pe`, `Pf`, `Pi`, `Po`, or `Ps`.
+the general Unicode categories  `Pc`, `Pd`, `Pe`, `Pf`, `Pi`, `Po`, or `Ps`.
 
 ## Tabs
 
@@ -402,8 +404,8 @@ as indentation with four spaces would:
 Normally the `>` that begins a block quote may be followed
 optionally by a space, which is not considered part of the
 content.  In the following case `>` is followed by a tab,
-which is treated as if it were expanded into spaces.
-Since one of theses spaces is considered part of the
+which is treated as if it were expanded into three spaces.
+Since one of these spaces is considered part of the
 delimiter, `foo` is considered to be indented six spaces
 inside the block quote context, so we get an indented
 code block starting with two spaces.
@@ -481,7 +483,7 @@ We can think of a document as a sequence of
 quotations, lists, headings, rules, and code blocks.  Some blocks (like
 block quotes and list items) contain other blocks; others (like
 headings and paragraphs) contain [inline](@) content---text,
-links, emphasized text, images, code, and so on.
+links, emphasized text, images, code spans, and so on.
 
 ## Precedence
 
@@ -5796,6 +5798,15 @@ we just have literal backticks:
 <p>`foo</p>
 ````````````````````````````````
 
+The following case also illustrates the need for opening and
+closing backtick strings to be equal in length:
+
+```````````````````````````````` example
+`foo``bar``
+.
+<p>`foo<code>bar</code></p>
+````````````````````````````````
+
 
 ## Emphasis and strong emphasis
 
@@ -5850,14 +5861,14 @@ characters that is not preceded or followed by a `_` character.
 
 A [left-flanking delimiter run](@) is
 a [delimiter run] that is (a) not followed by [Unicode whitespace],
-and (b) either not followed by a [punctuation character], or
+and (b) not followed by a [punctuation character], or
 preceded by [Unicode whitespace] or a [punctuation character].
 For purposes of this definition, the beginning and the end of
 the line count as Unicode whitespace.
 
 A [right-flanking delimiter run](@) is
 a [delimiter run] that is (a) not preceded by [Unicode whitespace],
-and (b) either not preceded by a [punctuation character], or
+and (b) not preceded by a [punctuation character], or
 followed by [Unicode whitespace] or a [punctuation character].
 For purposes of this definition, the beginning and the end of
 the line count as Unicode whitespace.
@@ -5936,7 +5947,7 @@ The following rules define emphasis and strong emphasis:
 7.  A double `**` [can close strong emphasis](@)
     iff it is part of a [right-flanking delimiter run].
 
-8.  A double `__` [can close strong emphasis]
+8.  A double `__` [can close strong emphasis] iff
     it is part of a [right-flanking delimiter run]
     and either (a) not part of a [left-flanking delimiter run]
     or (b) part of a [left-flanking delimiter run]
@@ -5977,7 +5988,7 @@ the following principles resolve ambiguity:
     `<em><em>...</em></em>`.
 
 14. An interpretation `<em><strong>...</strong></em>` is always
-    preferred to `<strong><em>..</em></strong>`.
+    preferred to `<strong><em>...</em></strong>`.
 
 15. When two potential emphasis or strong emphasis spans overlap,
     so that the second begins before the first ends and ends after
@@ -8319,11 +8330,11 @@ The link labels are case-insensitive:
 ````````````````````````````````
 
 
-If you just want bracketed text, you can backslash-escape the
-opening `!` and `[`:
+If you just want a literal `!` followed by bracketed text, you can
+backslash-escape the opening `[`:
 
 ```````````````````````````````` example
-\!\[foo]
+!\[foo]
 
 [foo]: /url "title"
 .