:: deftheorem Def27 defines .edgesOutOf GLIB_000:def 27 :
for G being _Graph
for X being set
for b₃ being Subset of (the_Edges_of G) holds
( b₃ = G .edgesOutOf X iff for e being set holds
( e in b₃ iff ( e in the_Edges_of G & (the_Source_of G) . e in X ) ) );