- ∀A,B.∀f: unary_morphism A B. injective ?? (quotiented_mor ?? f).
- #A; #B; #f; nwhd; #x; #x'; #H; nassumption.
-nqed.
\ No newline at end of file
+ ∀A,B.∀f: unary_morphism A B. injective ?? (Full_set ?) (quotiented_mor ?? f).
+ #A; #B; #f; nwhd; #x; #x'; #Hx; #Hx'; #K; nassumption.
+nqed.
+
+nrecord isomorphism (A) (B) (S: qpowerclass A) (T: qpowerclass B) : CProp[0] ≝
+ { iso_f:> unary_morphism A B;
+ f_sur: surjective ?? S T iso_f;
+ f_inj: injective ?? S iso_f
+ }.