README.md in ebnf-2.1.2 vs README.md in ebnf-2.1.3

@@ -1,12 +1,13 @@
 # EBNF 
 
 [EBNF][] parser and generic parser generator.
 
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 ## Description
 This is a [Ruby][] implementation of an [EBNF][] and [BNF][] parser and parser generator.
 
 ### [PEG][]/[Packrat][] Parser
@@ -90,10 +91,10 @@
 
 ### Writing Grammars
 
 The {EBNF::Writer} class can be used to write parsed grammars out, either as formatted text, or HTML. Because grammars are written from the Abstract Syntax Tree, represented as [S-Expressions][S-Expression], this provides a means of transforming between grammar formats (e.g., W3C [EBNF][] to [ABNF][]), although with some potential loss in semantic fidelity (case-insensitive string matching vs. case-sensitive matching).
 
-The formatted HTML results are designed to be appropriate for including in specifications.
+The formatted HTML results are designed to be appropriate for including in specifications. If the [Nokogumbo](https://rubygems.org/gems/nokogumbo) gem list available, the resulting HTML encoded grammar will also be validated.
 
 ### Parser Errors
 On a parsing failure, and exception is raised with information that may be useful in determining the source of the error.
 
 ## EBNF Grammar