L-functions for line graphs of semiregular bipartite graphs

We give the zeta functions and the complexities of a regular covering of a semiregular bipartite graph G and its line graph by using some characteristic polynomial and its derivative. Furthermore, we express the L-functions of the line graph of G in terms of some characteristic polynomial. As a corollary, we present another proof for a formula of the zeta function of the line graph of a regular covering of G.