let L be non empty satisfying_Sheffer_1 satisfying_Sheffer_2 satisfying_Sheffer_3 ShefferStr ; :: thesis: for p, y, w being Element of L holds (w | (y | (y | y))) | (w | p) = w
let p, y, w be Element of L; :: thesis: (w | (y | (y | y))) | (w | p) = w
w | w = w | (y | (y | y)) by SHEFFER1:def 14;
hence (w | (y | (y | y))) | (w | p) = w by Th132; :: thesis: verum