theorem Th88: :: SHEFFER2:88

for L being non empty satisfying_Sheffer_1 satisfying_Sheffer_2 satisfying_Sheffer_3 ShefferStr
for y, q, w being Element of L holds ((w | q) | ((y | y) | y)) | ((w | q) | (w | q)) = ((w | w) | (w | q)) | ((q | q) | (w | q))