Upyr or Upir ?

I know that on the wiki we spell it "upyr" but all over other webstites and the hemlock grove tumblr <-which I think theyve abandoned?? its spelled "upir" and I think in the book aswell has anyone read the book and knows how its supposed to be spelled? I know it sounds stupid but I think we should have it spelled right if were gonna be a encyclopedia for the show.