@article{MZ_1973__133_171943,
     author = {Walter Schempp and Bernd Dreseler},
     title = {Zonal {Approximation} {Processes.}},
     journal = {Mathematische Zeitschrift},
     pages = {81--92},
     publisher = {mathdoc},
     volume = {133},
     year = {1973},
     zbl = {0252.41022},
     url = {http://geodesic.mathdoc.fr/item/MZ_1973__133_171943/}
}