@article{10_4064_cm_58_1_11_15,
     author = {Carl Pomerance},
     title = {On the composition of the arithmetic functions \ensuremath{\sigma} and \ensuremath{\varphi}},
     journal = {Colloquium Mathematicum},
     pages = {11--15},
     publisher = {mathdoc},
     volume = {58},
     number = {1},
     year = {1989},
     doi = {10.4064/cm-58-1-11-15},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/cm-58-1-11-15/}
}