theorem Th158: :: SHEFFER2:158

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