@article{MZ_1976__152_172457,
     author = {Manohar L. Madan},
     title = {Null {Class} {Groups} of {Algebraic} {Function} {Fields.}},
     journal = {Mathematische Zeitschrift},
     pages = {59--66},
     publisher = {mathdoc},
     volume = {152},
     year = {1976},
     zbl = {0324.14004},
     url = {http://geodesic.mathdoc.fr/item/MZ_1976__152_172457/}
}