@article{JIS_2006__9_1_a7,
     author = {Shparlinski, Igor E.},
     title = {On the sum of iterations of the {Euler} function},
     journal = {Journal of integer sequences},
     publisher = {mathdoc},
     volume = {9},
     number = {1},
     year = {2006},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2006__9_1_a7/}
}