let G, H be AddGroup; :: thesis: for f being strict Morphism of G,H holds {f} is GroupMorphism_DOMAIN of G,H
let f be strict Morphism of G,H; :: thesis: {f} is GroupMorphism_DOMAIN of G,H
for x being Element of {f} holds x is strict Morphism of G,H by TARSKI:def 1;
hence {f} is GroupMorphism_DOMAIN of G,H by Th25; :: thesis: verum