Let G be a graph. If there exists E0 ⊂ E(G) such that (i) there
is no isolated vertex in G − E0 and (ii) γt(G − E0) > γt(G), then the edge set E0 is
called a total bondage edge set for G. If there is at least one total bondage edge set for
G, we define bt(G) = min{|E0| : E0 is a total bondage edge set of G}. Otherwise we put
bt(G) = ∞.