<li>Also from the <wikipedia>W3C</wikipedia>, a <ahref="https://www.w3.org/International/tutorials/language-decl/">tutorial "Declaring Language in XHTML and HTML"</a></li>
way to search subtags online in the registry</a> (some explanations are provided, but this tool is more useful if you know the concepts behind the registry)</li>
<li>Browse <ahref ="https://util.unicode.org/UnicodeJsps/languageid.jsp">language tags</a> and see their meaning</li>
<li>The subtag registry (version <em><lsr-version/></em>) in <ahref="registries.html">various formats</a></li>
<li>Martin Dürst's implementation in <wikipedianame="Ruby (programming language)">Ruby</wikipedia> is available as a <wikipedianame="RubyGems">Gem</wikipedia> named "langtag" at <wikipedia>RubyForge</wikipedia></li>
<li><ahref="philips-regexp.html">Addison Phillips' code</a>, as a <wikipedianame="Regular expression">regexp</wikipedia> for <wikipedianame="Java (programming language)">Java</wikipedia></li>
<li>The current standard: <ahref="https://www.rfc-editor.org/info/rfc5646">RFC 5646</a> and <ahref="https://www.rfc-editor.org/info/rfc4647">RFC 4647</a></li>