Text Encoding Inititative (TEI or TEI-XML)

TEI Guidelines for Electronic Text Encoding and Interchange: https://www.tei-c.org/release/doc/tei-p5-doc/en/html/index.html

The Journal of the Text Encoding Initiative (JTEI): https://journals.openedition.org/jtei/

Comic Book Markup Language (CBML)

About: http://dcl.ils.indiana.edu/cbml/

Article about CBML: http://www.digitalhumanities.org/dhq/vol/6/1/000117/000117.html