The Difference Between Intranet and Internet Design
http://www.useit.com/alertbox/9709b.html

Nielsen, Jakob
Alertbox
1997

Abstract:

Your intranet and your public website on the open Internet are two different information spaces and should have two different user interface designs. It is tempting to try to save design resources by reusing a single design, but it is a bad idea to do so because the two types of site differ along several dimensions.