@article{JIS_2009__12_8_a6,
     author = {Jim\'enez Urroz, J. and Yebra, J.Luis A.},
     title = {On the equation $a^x \equiv x\pmod{b^n}$},
     journal = {Journal of integer sequences},
     publisher = {mathdoc},
     volume = {12},
     number = {8},
     year = {2009},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2009__12_8_a6/}
}