% Mizar problem: t68_enumset1,enumset1,818,5 
fof(t68_enumset1, conjecture,  (! [A] :  (! [B] :  (! [C] :  (! [D] : k2_enumset1(A, B, C, D)=k2_enumset1(B, C, D, A)) ) ) ) ).
fof(dt_k2_enumset1, axiom, $true).
fof(l80_enumset1, axiom,  (! [A] :  (! [B] :  (! [C] :  (! [D] : k2_enumset1(A, B, C, D)=k2_enumset1(B, C, A, D)) ) ) ) ).
fof(t61_enumset1, axiom,  (! [A] :  (! [B] :  (! [C] :  (! [D] : k2_enumset1(A, B, C, D)=k2_enumset1(A, B, D, C)) ) ) ) ).
