@article{JIS_2010__13_7_a3,
     author = {Tang, Min},
     title = {Relatively prime sets and a phi function for subsets of $\{1, 2,\dots, n\}$},
     journal = {Journal of integer sequences},
     publisher = {mathdoc},
     volume = {13},
     number = {7},
     year = {2010},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2010__13_7_a3/}
}