These tutorials are authored as a set of DITA 1.2-conforming maps and topics using topic types from the DITA for Publishers project as configured for use in the DITA for Practitioners book from which these tutorials are drawn. I use OxygenXML as my day-to-day authoring environment. The HTML, PDF, and EPUB versions were produced using the DITA Open Toolkit. The EPUB plugin is currently available through the DITA for Publishers project.
Please report any comments, bug reports, or technical inaccuracies to me at firstname.lastname@example.org. Please include "DITA Tutorial" in the subject line so I know it's probably not spam. I'm also happy to discuss any aspect of the tutorial on the DITA users Yahoo! group, email@example.com.