@article{MOMA_1977__83_177803,
     author = {Paul Erd\"os and Ian Richards},
     title = {Density {Functions} for {Prime} and {Relatively} {Prime} {Numbers.}},
     journal = {Monatshefte f\"ur Mathematik},
     pages = {99--112},
     publisher = {mathdoc},
     volume = {83},
     year = {1977},
     zbl = {0355.10034},
     url = {http://geodesic.mathdoc.fr/item/MOMA_1977__83_177803/}
}