reserve x, y for set;
reserve D for non empty set;
reserve UN for Universe;
reserve C for Category;
reserve O for non empty Subset of the carrier of C;
reserve G,H for AddGroup;

theorem Th14:
  for F being GroupMorphism ex G,H st F is Morphism of G,H
proof
  let F be GroupMorphism;
  take G = the Source of F,H = the Target of F;
  dom(F) = G & cod(F) = H;
  hence thesis by Def12;
end;
