Canonical Text Services
Canonical Text Services identify and retrieve passages of text cited by canonical reference.
The Canonical (previously 'Classical') Text Services specification defines a network service for identifying texts and retrieving fragments of texts using notions of "work" and "citation" traditional in classical studies and other literary disciplines.
The Perseus Project also relies on CTS architecture, see .
Brief Guide to the Canonical Text Service (January 30, 2013)
A Gentle Introduction to CTS & CITE URNs (Casey Dué, D. Neel Smith, and Christopher W. Blackwell, October 2012)
A CiteULike CTS bibliography by Alison Babeu.
Older code and documentation addresses
The project also has a Sourceforge site, with more recent information: http://cts3.sourceforge.net/
There is a mailing list, too: https://lists.sourceforge.net/lists/listinfo/cts3-general