@article{GDZPPN002203553,
title = {Congruent subsets of infinite sets of natural numbers.},
journal = {Journal f\"ur die reine und angewandte Mathematik},
volume = {372},
year = {1986},
pages = {207-214},
zbl = {0575.10041},
url = {http://dml.mathdoc.fr/item/GDZPPN002203553}
}
Harzheim, Egbert; Erdös, Paul. Congruent subsets of infinite sets of natural numbers.. Journal für die reine und angewandte Mathematik, Tome 372 (1986) pp. 207-214. http://gdmltest.u-ga.fr/item/GDZPPN002203553/