Remark 2.2. Because H1 and H2 are subgraphs of G1 and G2, respectively, therefore
degH0 wi ≤ min{degG1
ui
, degG2
vi} for the vertex (ui
, vi) in the labeled glued
graph which is related to wi in H0
. Hence degG1✁✄¯
H0
G2
(ui
, vi) > 0.
Remark 2.3. Since the glued graph is an image of the labeled glued graph related
to it, the glued graph preserves the properties of its labeled glued graph.
Now, we state of the main rusult theorem.
Theorem 2.4. The glued graph of any two nontrivial connected graphs is Eulerian
if and only if the following conditions hold:
1.) the clones of the two original graphs contain all odd vertices in their two
original graphs,
2.) every even vertex in the clones of the two original graphs is obtained from
both odd or both even vertices in the two original graphs, and every odd vertex
in those clones is obtained from one odd and one even vertex in the two original
graphs.