I am an early-career mathematics-education researcher. Recently, I received a request for major revisions for a manuscript I had submitted on opportunities to learn provided by undergraduate mathematics calculus textbooks.
One of the issues I need to address is explaining the theoretical contribution of the study reported in the manuscript. I am not sure how to address this issue. I guess my greatest challenge is that I don't know what a theoretical contribution is in mathematics education. I would greatly appreciate if someone could explain what the reviewers mean or rather expect in my response. Suggestions for resources to read on this subject are welcome too.