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 Th13:
  for F being strict Morphism of G,H ex f being Function of G,H st
  F = GroupMorphismStr(# G,H,f#)
proof
  let F be strict Morphism of G,H;
  consider f being Function of G,H such that
A1: F = GroupMorphismStr(# G,H,f#) and
  f is additive by Th12;
  take f;
  thus thesis by A1;
end;
