"topic-oriented authoring" with "DITA" = "Darwin Information Typing Architecture"

• https://en.wikipedia.org/wiki/Darwin_Information_Typing_Architecture
• http://dita.xml.org/
• http://tech.groups.yahoo.com/group/dita-users/

DITA for Print (A tutorial introduction to the DITA Open Toolkit FO/PDF stylesheets):

• downloadable examples
• errata
• …

DITA for Practitioners Volume 1: "Architecture and Technology" (comprehensive guide to DITA for implementors):

• http://xmlpress.net/publications/dita/practitioners-1/
• http://dita4practitioners.org – "DITA for Practitioners Volume 1"'s companion website
• http://dita4practitioners.com/forums
• …