fact: Definition Pullback_law4 := forall (r : C) (t1 : r --> a) (t2 : r --> c) (pe : Pullback_eq1 t1 t2) (g : r --> Fibred_prod), Pullback_eq2 t1 Fibred_p g -> Pullback_eq2 t2 Fibred_q g -> g =_S Pb_diese pe.
imports: CatProperty