@article{JRAM_1990__406_153223,
     author = {Jin Nakagawa},
     title = {Binary forms and unramified {An-extensions} of quadratic fields.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {167--178},
     year = {1990},
     volume = {406},
     zbl = {0693.12008},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1990__406_153223/}
}