XML fragment serialization algorithm links to https://w3c.github.io/DOM-Parsing/#dfn-xml-fragment-serialization-algorithm

Parsing concepts: a fragment parsing context; the HTML fragment parsing algorithm; the HTML fragment serialization algorithm; HTML parser; parsing XHTML documents; the XML fragment parsing algorithm; the XML fragment serialization algorithm; XML parser;

[XML fragment serialization algorithm] links to https://www.w3.org/TR/html5/single-page.html#xml-fragment-serialization-algorithm

It probably should be https://html.spec.whatwg.org/#serialising-xhtml-fragments