@article{PORMA_1956__15_3_114773,
     author = {Swingle, Paul M.},
     title = {Local properties and sums of trajectories},
     journal = {Portugaliae mathematica},
     pages = {89--103},
     publisher = {mathdoc},
     volume = {15},
     number = {3},
     year = {1956},
     mrnumber = {0087928},
     zbl = {0071.38503},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1956__15_3_114773/}
}