Canonical cfMorph_additive := Additive cfMorph_is_linear.
Canonical cfMorph_linear := Linear cfMorph_is_linear.
Fact cfMorph_is_multiplicative : multiplicative cfMorph.
Canonical cfMorph_rmorphism := AddRMorphism cfMorph_is_multiplicative.
Canonical cfMorph_lrmorphism := [lrmorphism of cfMorph].
Hypothesis sGD : G \subset D.

Lemma cfker_morph_im phi : f @* cfker (cfMorph phi) = cfker phi.