Spanning sets for Moebius vertex algebras satisfying arbitrary   difference conditions
  Spanning sets for vertex operator algebras satisfying difference-zero and difference-one conditions have been extensively studied in the recent years. In this paper, we extend these results. More specifically, we show that for a suitably chosen generating set, any N-graded Moebius vertex algebra is spanned by monomials satisfying a difference-N ordering condition. 
Geoffrey Buhl, Gizem Karaali