theorem Th74: :: SHEFFER2:74

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