On universal gradings, versal gradings and Schurian generated categories
  Categories over a field $k$ can be graded by different groups in a connected way; we consider morphisms between these gradings in order to define the fundamental grading group. We prove that this group is isomorphic to the fundamental group \`a la Grothendieck as considered in previous papers. In case the $k$-category is Schurian generated we prove that a universal grading exists. Examples of non Schurian generated categories with universal grading, versal grading or none of them are considered. 
Claude Cibils, Maria Julia Redondo and Andrea Solotar
math.CT math.RA