@article{MZ_1973__135_172010,
     author = {Dragomir Z. Djokovic},
     title = {Level of a {Field} and the {Number} of {Square} {Classes.}},
     journal = {Mathematische Zeitschrift},
     pages = {267--270},
     publisher = {mathdoc},
     volume = {135},
     year = {1973},
     url = {http://geodesic.mathdoc.fr/item/MZ_1973__135_172010/}
}