  If H is a finite dimensional Hopf algebra, C. Cibils and M. Rosso found an
algebra X having the property that Hopf bimodules over H^* coincide with left
X-modules. We find two other algebras, Y and Z, having the same property;
namely, Y is the "two-sided crossed product" H^*#(H\otimes H^{op})# H^{* op}
and Z is the "diagonal crossed product" (H^*\otimes H^{*op})\bowtie (H\otimes
H^{op}) (both concepts are due to F. Hausser and F. Nill). We also find
explicit isomorphisms between the algebras X, Y, Z.
