theorem Th59: :: GLIB_013:59

for G1, G2 being _Graph
for F being PGraphMapping of G1,G2 st F is onto & F is semi-Dcontinuous & dom (F _V) = the_Vertices_of G1 holds
( G2 .minInDegree() c= G1 .minInDegree() & G2 .minOutDegree() c= G1 .minOutDegree() )