theorem Th55: :: GRAPH_3:55

for X being set
for G being finite Graph
for v being Vertex of G st Degree (v,X) <> 0 & ( for v being Vertex of G holds Degree (v,X) is even ) holds
for c being Element of X -CycleSet v holds
( not c is empty & rng c c= X & v in G -VSet (rng c) )