Reenskaug, Trygve (1996). "Working with Objects: OOram Framework Design Principles" (PDF). Taskon, Norway. (Presented at OOPSLA 1996 Workshop: Exploration of Framework Design Principles) http://home.ifi.uio.no/trygver/1996/Frameworks/frameworks.pdf
Terje Totland (1997). 5.2.8 Object-Oriented role analysis and modeling (OOram) Thesis, Norwegian University of Science and Technology (NTNU), Trondheim. http://www.idi.ntnu.no/grupper/su/publ/html/totland/ch0528.htm
(Reenskaug, 1996:60)
Terje Totland (1997). 5.2.8 Object-Oriented role analysis and modeling (OOram) Thesis, Norwegian University of Science and Technology (NTNU), Trondheim. http://www.idi.ntnu.no/grupper/su/publ/html/totland/ch0528.htm