Some of our junior/senior students are considering graduate school, however, most of our students come from low socioeconomic backgrounds.  and cannot afford the study materials  We had planned on purchasing GRE prep books as a department to keep on hand in the library, but with COVID, this has complicated things. Does any one have resources or suggestions for open source study materials for the GRE that you or your school has used before? As of right now we are having face-to-face classes but bracing for the real potential of moving 100% online so ideally we are looking for any suggestions/resources the students can access at home as well.