Definition cfDprodl := cfSdprod (dprodWsdC KxH).
Definition cfDprod phi psi := cfDprodl phi * cfDprodr psi.
Canonical cfDprodl_additive := [additive of cfDprodl].
Canonical cfDprodl_linear := [linear of cfDprodl].
Canonical cfDprodl_rmorphism := [rmorphism of cfDprodl].
Canonical cfDprodl_lrmorphism := [lrmorphism of cfDprodl].
Canonical cfDprodr_additive := [additive of cfDprodr].
Canonical cfDprodr_linear := [linear of cfDprodr].
Canonical cfDprodr_rmorphism := [rmorphism of cfDprodr].
Canonical cfDprodr_lrmorphism := [lrmorphism of cfDprodr].

Lemma cfker_dprodr psi : K \x cfker psi = cfker (cfDprodr psi).