@article{MZ_1973__130_171865,
     author = {Thomas F. Bickel},
     title = {Circles in {(B,} {N)-Groups.}},
     journal = {Mathematische Zeitschrift},
     pages = {249--254},
     publisher = {mathdoc},
     volume = {130},
     year = {1973},
     zbl = {0239.20049},
     url = {http://geodesic.mathdoc.fr/item/MZ_1973__130_171865/}
}