theorem Th56: :: GLIB_013:56

for G1, G2 being _Graph
for F being PGraphMapping of G1,G2 st F is directed & F is weak_SG-embedding holds
( G1 .supInDegree() c= G2 .supInDegree() & G1 .supOutDegree() c= G2 .supOutDegree() )