intros a b p q H'; inversion_clear H'; trivial.
Qed.

Theorem ltp_eqp_comp :
forall p q r s,
ltP (A:=A) (n:=n) ltM p q ->
canonical A0 eqA ltM p ->
canonical A0 eqA ltM q -> eqP p r -> eqP q s -> ltP (A:=A) (n:=n) ltM r s.