I've written 2 papers one was more or less an expository on a difficult topic in group theory and the other one I just finished writing is a paper that introduces the basic concepts in elementary measure theory and then gives an original result from it. I submitted the first one to a journal but was rejected the next day because I don't have a sponsor. The journal only required 1/3 of student authorship which means 2/3 of the paper was done by the sponsor whereas my paper was 100% student work. I think it's unfair that these journals are supposed to promote student research and make it impossible or people like me who are doing all the work on their own to submit a paper. I've searched dozens of journals and they all have this sponsor policy, but I was wondering if anyone knows of one where that's not the case or has any advice. The whole thing is pretty frustrating considering the work I put into each paper.