The Online Books Page

XML (Document markup language)

See also what's at Wikipedia, your library, or elsewhere.

• Document markup languages

• Extendible Markup Language (Document markup language)
• eXtensible Markup Language (Document markup language)

• Processing XML With Java: A Guide to SAX, DOM, JDOM, JAXP, and TrAX, by Elliotte Rusty Harold (HTML with commentary at cafeconleche.org)
• Relax NG, by Eric Van der Vlist (HTML at books.xmlschemata.org)
• DocBook: The Definitive Guide, by Norman Walsh and Leonard Muellner (HTML and SGML at docbook.org)

Items below (if any) are from related and broader terms.

• Creating and Documenting Electronic Texts: A Guide to Good Practice (2000), by Alan S. Morrison, Michael Popham, and Karen Wikander (HTML in the UK)

• Encoded Archival Description Tag Library (current version, which at time of cataloging was EAD3 1.1.0, edition 2018), by Society of American Archivists Technical Subcommittee for Encoded Archival Description (HTML and PDF with commentary at loc.gov)
• Encoded Archival Description Tag Library (version 2002, revised edition (but later superseded); Chicago: Society of American Archivists, 2003), by Society of American Archivists Encoded Archival Description Working Group and Library of Congress Network Development and MARC Standards Office (PDF at archivists.org)

• Pro HTML5 Programming (interactive online edition, ca. 2011), by Peter Lubbers, Brian Albers, Frank Salim, and Tony Pye (HTML at jensimmons.com)
• Dive Into HTML5 (later published as "HTML5: Up and Running"; 2010), by Mark Pilgrim (multiple formats at archive.org)
• HTML5 for Web Designers (c2010), by Jeremy Keith (HTML with commentary at html5forwebdesigners.com)
• Spinning the Web: A Guide to Serving Information on the Internet (first edition, 1994), by Andrew Ford (HTML at Wayback Machine)
• How to Code in HTML5 and CSS3, by Damian Wielgosik (multiple formats with commentary at howtocodeinhtml.com)
• Internet Publishing with Acrobat (c1996), by Gordon Kent (PDF at Wayback Machine)
• Embedding Perl in HTML with Mason, by Dave Rolsky and Ken Williams (HTML with commentary at houseabsolute.com)

• How to Code in HTML5 and CSS3, by Damian Wielgosik (multiple formats with commentary at howtocodeinhtml.com)

• Scalable and Modular Architecture for CSS, by Jonathan Snook (multiple formats with commentary at smacss.com)

• An Introduction to Ontology Engineering (c2020), by C. Maria Keet (PDF in South Africa)

• Validating RDF Data (c2018), by Jose Emilio Labra Gayo, Eric Prud'hommeaux, Iovka Boneva, and Dimitris Kontokostas (illustrated HTML with commentary at validatingrdf.com)
• Practical Semantic Web and Linked Data Applications: Common Lisp Edition (c2010), by Mark Watson (PDF at markwatson.com)
• Practical Semantic Web and Linked Data Applications: Java, Scala, Clojure, and JRuby Edition (c2010), by Mark Watson (PDF at markwatson.com)

• Developing SGML DTDs: From Text to Model to Markup (c1996), by Eve Maler and Jeanne El Andaloussi (HTML with commentary at xmlgrrl.com)
• DocBook: The Definitive Guide, by Norman Walsh and Leonard Muellner (HTML and SGML at docbook.org)

• SVG Essentials (c2002), by J. David Eisenberg (illustrated HTML with commentary at oreilly.com)