@article{JIS_2009__12_2_a1,
     author = {T\'oth, L\'aszl\'o},
     title = {A gcd-sum function over regular integers modulo $n$},
     journal = {Journal of integer sequences},
     publisher = {mathdoc},
     volume = {12},
     number = {2},
     year = {2009},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2009__12_2_a1/}
}