Don't be fooled by those who deliver links on .edu.com/ domains as been .EDU backlinks
Don't be fooled by those who check only the domain / homepage PageRank. We are talking here about The ACTUAL page PageRank
We can manage unlimited ULR and KEYWORD but keep in mind that we are talking about 320 Backlinks in total so the number of ULR * Keywords should not be grather than 320