let L be non empty satisfying_Sheffer_1 satisfying_Sheffer_2 satisfying_Sheffer_3 ShefferStr ; :: thesis: for p, w being Element of L holds (w | p) | (w | (p | p)) = w
let p, w be Element of L; :: thesis: (w | p) | (w | (p | p)) = w
(p | p) | w = w | (p | p) by Th83;
hence (w | p) | (w | (p | p)) = w by Th102; :: thesis: verum