@article{PIM_1991_N_S_50_64_a8,
     author = {Barry J. Powell and Tibor \v{S}al\'at},
     title = {Convergence of {Subseries} of the {Harmonic} {Series} and {Asymptotic} {Densities} of {Sets} of {Positive} {Integers}},
     journal = {Publications de l'Institut Math\'ematique},
     pages = {60 },
     publisher = {mathdoc},
     volume = {_N_S_50},
     number = {64},
     year = {1991},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PIM_1991_N_S_50_64_a8/}
}