@article{GDZPPN002332795, title = {Geometry of normed bilinear maps and the 16-square problem.}, journal = {Mathematische Annalen}, volume = {283}, year = {1989}, pages = {437-448}, zbl = {0649.10015}, url = {http://dml.mathdoc.fr/item/GDZPPN002332795} }
Lam, K.Y.; Yiu, P.Y.H. Geometry of normed bilinear maps and the 16-square problem.. Mathematische Annalen, Tome 283 (1989) pp. 437-448. http://gdmltest.u-ga.fr/item/GDZPPN002332795/