@article{10_4064_cm130_1_11,
     author = {Kevin Broughan and Kevin Ford and Florian Luca},
     title = {On square values of the product of the {Euler} totient and sum of divisors functions},
     journal = {Colloquium Mathematicum},
     pages = {127--137},
     publisher = {mathdoc},
     volume = {130},
     number = {1},
     year = {2013},
     doi = {10.4064/cm130-1-11},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/cm130-1-11/}
}