@article{MZ_1968__103_170895,
     author = {Henri Joris},
     title = {On {Bochner's} {Theorem} on the {Critical} {Index} for {Multiple} {Fourier} {Series.}},
     journal = {Mathematische Zeitschrift},
     pages = {61--66},
     publisher = {mathdoc},
     volume = {103},
     year = {1968},
     zbl = {0165.39603},
     url = {http://geodesic.mathdoc.fr/item/MZ_1968__103_170895/}
}