@article{MZ_1935__39_168557,
     author = {M.D. and Pollard, S. Kennedy},
     title = {Upper and lower integrals},
     journal = {Mathematische Zeitschrift},
     pages = {432--454},
     publisher = {mathdoc},
     volume = {39},
     year = {1935},
     zbl = {60.0205.02},
     url = {http://geodesic.mathdoc.fr/item/MZ_1935__39_168557/}
}