@article{10_1007_s10587_011_0079_x,
     author = {Somer, Lawrence and K\v{r}{\'\i}\v{z}ek, Michal},
     title = {The structure of digraphs associated with the congruence $x^k\equiv y \pmod n$},
     journal = {Czechoslovak Mathematical Journal},
     pages = {337--358},
     publisher = {mathdoc},
     volume = {61},
     number = {2},
     year = {2011},
     doi = {10.1007/s10587-011-0079-x},
     mrnumber = {2905408},
     zbl = {1249.11006},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.1007/s10587-011-0079-x/}
}