@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/