@article{10_4064_aa_8_4_349_356,
     author = {N. de Bruijn and J. van Lint},
     title = {On the number of integers \ensuremath{\leq} x whose prime factors divide n},
     journal = {Acta Arithmetica},
     pages = {349--356},
     publisher = {mathdoc},
     volume = {8},
     number = {4},
     year = {1962},
     doi = {10.4064/aa-8-4-349-356},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/aa-8-4-349-356/}
}