Here is a list of the articles that I summarized and the reviews that I did along with Shelia on this topic.
Ten core principles for designing effective learning environments: Insights from brain research and pedagogical theory.
Toward constructivism for adult learners in online learning environments
Making it real online: Distance learning for high school students
Evaluating online teaching
The distancing question in online learning.
Interaction in online learning environments; A review of the literature