July 10, 2002 at 2:43 PM
Here is a very old (1997) article I dug up on Google: Virtual Hierarchies and Virtual Networks: some lessons from hypermedia usability research applied to the World Wide Web by Pauline Smith from Nottingham Trent University as well as I.A. Newman and L.M. Parks from Loughborough University. Quite lengthy, out of date and hard to navigate, but it's interesting to see such an old study on navigation.