Problems in Navigating Online Help: Clues from User Search Patterns
http://www.winwriters.com/articles/navigation/

Krull, Robert and Angela Eaton
WritersUA
2005

Abstract:

The largest problem our participants had in using the help system wasn't in processing the procedural information in the help, but rather finding the correct help topic, a topic generally unaddressed in the literature on how to write a help system. Specifically, participants had difficulty in searching for topics because their terminology differed from the terminology used by the help system, and they became lost in the unclear structure of the system.