theorem Th151: :: SHEFFER2:151

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