@article{10_4064_aa_12_4_321_332,
     author = {Ralph Alexander},
     title = {Density and multiplicative structure of sets of integers},
     journal = {Acta Arithmetica},
     pages = {321--332},
     publisher = {mathdoc},
     volume = {12},
     number = {4},
     year = {1966},
     doi = {10.4064/aa-12-4-321-332},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/aa-12-4-321-332/}
}