theorem Th75: :: SHEFFER2:75

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