@article{TRSPY_1976_142_a17, author = {S. S. Ryshkov}, title = {On the problem of determining perfect quadratic forms of several variables}, journal = {Informatics and Automation}, pages = {215--239}, publisher = {mathdoc}, volume = {142}, year = {1976}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/TRSPY_1976_142_a17/} }