@article{JIS_2010__13_4_a7,
     author = {Zhang,  Deyu and Zhai,  Wenguang},
     title = {Mean values of a gcd-sum function over regular integers modulo \(n\)},
     journal = {Journal of integer sequences},
     year = {2010},
     volume = {13},
     number = {4},
     zbl = {1219.11143},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2010__13_4_a7/}
}