Definition 1.5 A sesquivalent graph is a simple graph, each component of which is regular
and has the degree 1 or 2; in the other words, the components are single edges or cycles.
Definition 1.6 If Γ is a subgraph of a graph G such that V (Γ) = V (G), then Γ is said to be
a spanning subgraph of the graph G.
Theorem 1.7 [4] Let A(G) be the adjacency matrix of a graph G. Then
det(A(G)) = X
Γ
(−1)r(Γ)(2)s(Γ)
where the summation is over all sesquivalent spanning subgraphs Γ of G with c(Γ) = the
number of components of the graph Γ , r(Γ) = |V (Γ)|−c(Γ) and s(Γ) = |E(Γ)|−|V (Γ)|+c(Γ).