The DITA Reference.

The official specification on the DITA standard.

An article from: Technical Communication, by Michael Priestley, Gretchen Hargis, Susan Carpenter. Avaialble from Amazon.

For a better understanding of DITA, please read the recent series of articles on DITA that were published in Arbortext's XML Publishing Network newsletter:

Wikipedia,  the free encyclopedia, describes DITA as "an XML-based architecture for authoring, producing, and delivering technical information. The architecture and a related DTD and a W3C-Schema was developed by IBM ... Unlike book-oriented approaches that are based on chapters and pages, DITA uses topics - small chunks of information that can be easily reused across various contexts and deliverables. DITA also has built-in extensibility support, meaning you can customize document type definitions (or DTDs) without breaking compatibility with existing applications and processes.