@article{JRAM_1970__245_151053,
     author = {Hans J. Sperling},
     title = {On the real singularities of the {N-body} problem.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {15--40},
     publisher = {mathdoc},
     volume = {245},
     year = {1970},
     zbl = {0207.23301},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1970__245_151053/}
}