@article{00530103,
title = {The number of real quadratic fields having units of negative norm.},
journal = {Experimental Mathematics},
volume = {2},
year = {1993},
pages = {121-136},
doi = {10.1080/10586458.1993.10504272},
zbl = {0792.11041},
language = {en},
url = {http://dml.mathdoc.fr/item/00530103}
}
Stevenhagen, Peter. The number of real quadratic fields having units of negative norm.. Experimental Mathematics, Tome 2 (1993) pp. 121-136. doi : 10.1080/10586458.1993.10504272. http://gdmltest.u-ga.fr/item/00530103/