@article{00032149,
title = {Convergence of subseries of the harmonic series and asymptotic densities of sets of positive integers.},
journal = {Publications de l'Institut Math\'ematique. Nouvelle S\'erie},
volume = {50(64)},
year = {1991},
pages = {60-70},
zbl = {0745.11008},
language = {en},
url = {http://dml.mathdoc.fr/item/00032149}
}
Powell, Barry J.; Šalát, Tibor. Convergence of subseries of the harmonic series and asymptotic densities of sets of positive integers.. Publications de l'Institut Mathématique. Nouvelle Série, Tome 50(64) (1991) pp. 60-70. http://gdmltest.u-ga.fr/item/00032149/