@article{JIS_2008__11_2_a5,
     author = {Tanigawa, Yoshio and Zhai, Wenguang},
     title = {On the gcd-sum function},
     journal = {Journal of integer sequences},
     publisher = {mathdoc},
     volume = {11},
     number = {2},
     year = {2008},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2008__11_2_a5/}
}