Deletion of Borda fixed point

Comment: I looked into it a bit. The first two links seem to lead to a now defunct preprint server, similar to the arXiv. The last two links are books published by Dutch University Press. I don't know this publisher, but it is not affiliated with any Dutch university as far as I can tell. I did not find evidence that any of these publications are peer-reviewed. Hence, I think they are not |reliable sources and that the article should be deleted
Stance: delete
Cited policy: Wikipedia:Reliable sources (WP:RS)