@article{MZ_1928__28_168046,
     author = {G. H., und J. Hardy and J. E. Littlewood},
     title = {A convergence criterion for {Fourier} series},
     journal = {Mathematische Zeitschrift},
     pages = {612--634},
     publisher = {mathdoc},
     volume = {28},
     year = {1928},
     zbl = {54.0301.03},
     url = {http://geodesic.mathdoc.fr/item/MZ_1928__28_168046/}
}