@article{CMH_1986__61_140042,
     author = {Y.-F. S. P\'etermann},
     title = {Changes of sign of error terms related to {Euler's} function and to divisor functions.},
     journal = {Commentarii mathematici Helvetici},
     pages = {84--101},
     publisher = {mathdoc},
     volume = {61},
     year = {1986},
     zbl = {0613.10037},
     url = {http://geodesic.mathdoc.fr/item/CMH_1986__61_140042/}
}