"For the past ten years, Richard Mayer and his colleagues at the University of California at Santa Barbara have conducted a series of controlled experiments on how to best use audio, text, and graphics to optimize learning in multimedia. Six media element principles can be defined based on Mayer’s work. What follows is a summary of these principles along with supporting examples, psychological rationale, and research."
I like these principles (and I like that there is some research to establish why they work)
Not enough references, and not direct references, which is what my "yet to be convinced" colleagues are looking for ... but the principles are logical and probably good starting points for a bit of further reading and discussion in development workshops for professional development of higher ed teachers