theorem Th117: :: SHEFFER2:117

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