theorem Th9: :: RINGCAT1:9

for G1, G2, G3, G4 being Ring
for f being Morphism of G1,G2
for g being Morphism of G2,G3
for h being Morphism of G3,G4 st G1 <= G2 & G2 <= G3 & G3 <= G4 holds
h * (g * f) = (h * g) * f