Rena M. Palloff and Keith Pratt, “Making the Transition: Helping Teachers to Teach Online”
This paper was presented at the EDUCAUSE 2000 conference in Nashville, TN (October 10-13, 2000).
This document was originally published back in 2004 by the Sloan Consortium. It covers the interaction of Social Presence, Cognitive Presence, and Teaching Presence. It also has an excellent overview of the relevant literature and bibliography.
The PDF is available here: Swan, Relationships Between Interactions and Learning In Online Environments.