theorem Th4: :: GLIB_000:4

for G being _Graph holds
( dom (the_Source_of G) = the_Edges_of G & dom (the_Target_of G) = the_Edges_of G & rng (the_Source_of G) c= the_Vertices_of G & rng (the_Target_of G) c= the_Vertices_of G ) by FUNCT_2:def 1;