“…For a right H-comodule algebra (A, ρ, φ ρ ), we show that the tensor functor − ⊗ k H is a comonad on the category A M H and we consider the category of two-sided Hopf modules Other forms of adjoint functors to −⊗ k H are obtained by defining Hausser-Nill and BulacuCaenepeel type coinvariants for this category (following [6,5], [9]). The relationship between these is explicitly described.…”