@article{PMF_1937_45_1_a4,
     author = {Estermann, T.},
     title = {On the representations of a number as a sum of squares},
     journal = {Prace Matematyczno-Fizyczne},
     pages = {93--125},
     publisher = {mathdoc},
     volume = {45},
     number = {1},
     year = {1937},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PMF_1937_45_1_a4/}
}