@article{JRAM_1977__289_151820,
     author = {G. Prins and R.A. Razen and F.J. Schnitzer},
     title = {On {Hall's} condition in transversal theory.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {85--95},
     publisher = {mathdoc},
     volume = {289},
     year = {1977},
     zbl = {0341.05003},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1977__289_151820/}
}