@article{JRAM_1970__245_151058,
     author = {Dimitrije Ugrin-Sparac},
     title = {Lower bounds for sums of powers of different natural numbers expressed as functions of the sum of these numbers.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {74--80},
     publisher = {mathdoc},
     volume = {245},
     year = {1970},
     zbl = {0206.05503},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1970__245_151058/}
}