Instance paco4_inst  T0 T1 T2 T3 (gf : rel4 T0 T1 T2 T3->_) r x0 x1 x2 x3 : paco_class (paco4 gf r x0 x1 x2 x3) :=
{ pacoacc    := paco4_acc gf;
  pacomult   := paco4_mult gf;
  pacofold   := paco4_fold gf;
  pacounfold := paco4_unfold gf }.Definition monotone4_2 T0 T1 T2 T3 (gf: rel4 T0 T1 T2 T3 -> rel4 T0 T1 T2 T3 -> rel4 T0 T1 T2 T3) :=
  forall x0 x1 x2 x3 r_0 r_1 r'_0 r'_1 (IN: gf r_0 r_1 x0 x1 x2 x3) (LE_0: r_0 <4= r'_0)(LE_1: r_1 <4= r'_1), gf r'_0 r'_1 x0 x1 x2 x3.

Theorem paco4_2_1_acc: forall l r_0 r_1 (OBG: forall rr (INC: r_1 <4= rr) (CIH: l <_paco_4= rr), l <_paco_4= paco4_2_1 gf_0 gf_1 r_0 rr), l <4= paco4_2_1 gf_0 gf_1 r_0 r_1.