Circulant digraphs determined by their spectra

Inspired by Ádámʹs conjecture the isomorphism problem of circulant digraphs is widely investigated. In the literature, the spectrum method was to solve the isomorphism problem for the circulants of prime-power order by some people. In this paper, we develop the spectrum method to characterize the circulant digraphs of orders pa and paqb, where p and q are distinct primes.