@article{10_4064_aa_26_3_265_272,
     author = {Carl Pomerance},
     title = {On the congruences $\ensuremath{\sigma}(n) \ensuremath{\equiv} a (mod n)$ and $n \ensuremath{\equiv} a (mod \ensuremath{\varphi}(n))$},
     journal = {Acta Arithmetica},
     pages = {265--272},
     publisher = {mathdoc},
     volume = {26},
     number = {3},
     year = {1974},
     doi = {10.4064/aa-26-3-265-272},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/aa-26-3-265-272/}
}