@article{10_4064_cm6880_6_2016,
     author = {Jean-Marie De Koninck and Imre K\'atai},
     title = {On the $k$-fold iterate of the sum of divisors function},
     journal = {Colloquium Mathematicum},
     pages = {247--255},
     publisher = {mathdoc},
     volume = {147},
     number = {2},
     year = {2017},
     doi = {10.4064/cm6880-6-2016},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/cm6880-6-2016/}
}