Ideal classes of three dimensional Sklyanin algebras
  In this paper we classify graded reflexive ideals, up to isomorphism and shift, in certain three dimensional Artin-Schelter regular algebras. This classification is similar to the classification of right ideals in the first Weyl algebra, a problem that was completely settled recently. The situation we consider is substantially more complicated however. 
K. De Naeghel, M. Van den Bergh