let L be non empty satisfying_Sheffer_1 satisfying_Sheffer_2 satisfying_Sheffer_3 ShefferStr ; :: thesis: for p, w being Element of L holds p = ((w | w) | p) | (((w | w) | (w | w)) | p)
let p, w be Element of L; :: thesis: p = ((w | w) | p) | (((w | w) | (w | w)) | p)
(p | p) | (p | (w | (w | w))) = p by Th72;
hence p = ((w | w) | p) | (((w | w) | (w | w)) | p) by Th95; :: thesis: verum