An excellent article on open source resources and the example of a teacher at the Univ. California who built his repository together with his students along the years – https://www.edsurge.com/news/2017-02-08-a-growing-but-controversial-idea-in-open-access-textbooks-let-students-help-write-them
OER should by now be generalized but unfortunatelly publishers have delayed the process.
Ida Brandão Space for MOOCs 