@article{BUMI_1999_8_2B_2_a14,
     author = {Mortola, Stefano and Peirone, Roberto},
     title = {The sum of periodic functions},
     journal = {Bollettino della Unione matematica italiana},
     pages = {393--396},
     publisher = {mathdoc},
     volume = {Ser. 8, 2B},
     number = {2},
     year = {1999},
     zbl = {0961.26005},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/BUMI_1999_8_2B_2_a14/}
}