theorem Th140: :: SHEFFER2:140

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