@article{JIS_2008__11_5_a7,
     author = {Ayad, Mohamed and Kihel, Omar},
     title = {On the number of subsets relatively prime to an integer},
     journal = {Journal of integer sequences},
     publisher = {mathdoc},
     volume = {11},
     number = {5},
     year = {2008},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2008__11_5_a7/}
}