@article{10_1017_S001708959997026X,
     author = {KUKSOV, DMITRI},
     title = {Cogrowth series of free products of finite and free groups},
     journal = {Glasgow mathematical journal},
     pages = {19--31},
     year = {1999},
     volume = {41},
     number = {1},
     doi = {10.1017/S001708959997026X},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S001708959997026X/}
}