On the generators of the canonical module of a Hibi ring: a criterion of   level property and the degrees of generators
  In this paper, we study the minimal generating system of the canonical module of a Hibi ring. Using the results, we state a characterization of a Hibi ring to be level. We also give a characterization of a Hibi ring to be of type 2. Further, we show that the degrees of the elements of the minimal generating system of the canonical module of a Hibi ring form a set of consecutive integers. 
Mitsuhiro Miyazaki
math.AC