@article{1255631814,
author = {De Bruijn, N. G.},
title = {On the number of integers $\leqq x$ whose prime factors divide $n$},
journal = {Illinois J. Math.},
volume = {6},
number = {1},
year = {1962},
pages = { 137-141},
language = {en},
url = {http://dml.mathdoc.fr/item/1255631814}
}
De Bruijn, N. G. On the number of integers $\leqq x$ whose prime factors divide $n$. Illinois J. Math., Tome 6 (1962) no. 1, pp. 137-141. http://gdmltest.u-ga.fr/item/1255631814/