@article{1183415369, author = {Thompson, H. D.}, title = {Focal Properties of Surfaces of the Second Order}, journal = {Bull. Amer. Math. Soc.}, volume = {4}, number = {8}, year = {1898}, pages = { 405-407}, language = {en}, url = {http://dml.mathdoc.fr/item/1183415369} }
Thompson, H. D. Focal Properties of Surfaces of the Second Order. Bull. Amer. Math. Soc., Tome 4 (1898) no. 8, pp. 405-407. http://gdmltest.u-ga.fr/item/1183415369/