@article{MZ_1969__112_171250,
     author = {Gordon M. Petersen},
     title = {Factor {Sequences} for {Summability} {Matrices.}},
     journal = {Mathematische Zeitschrift},
     pages = {389--392},
     publisher = {mathdoc},
     volume = {112},
     year = {1969},
     zbl = {0192.41702},
     url = {http://geodesic.mathdoc.fr/item/MZ_1969__112_171250/}
}