@article{10_1007_s10587_012_0028_3,
     author = {Ahmad, Uzma and Syed, Husnine},
     title = {On the heights of power digraphs modulo $n$},
     journal = {Czechoslovak Mathematical Journal},
     pages = {541--556},
     publisher = {mathdoc},
     volume = {62},
     number = {2},
     year = {2012},
     doi = {10.1007/s10587-012-0028-3},
     mrnumber = {2990193},
     zbl = {1265.05274},
     language = {en},
     url = {https://geodesic-test.mathdoc.fr/articles/10.1007/s10587-012-0028-3/}
}