@article{MZ_1981__178_173109,
     author = {G\"unter Baigger},
     title = {Summability of {Martingales} with {Two-dimensional} {Parameter.}},
     journal = {Mathematische Zeitschrift},
     pages = {381--386},
     publisher = {mathdoc},
     volume = {178},
     year = {1981},
     zbl = {0451.60048},
     url = {http://geodesic.mathdoc.fr/item/MZ_1981__178_173109/}
}