@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},
     publisher = {mathdoc},
     volume = {13},
     number = {4},
     year = {2010},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2010__13_4_a7/}
}