@article{1248269777,
author = {Filipin, Alan},
title = {On the Size of Sets in Which $xy + 4$ is Always a Square},
journal = {Rocky Mountain J. Math.},
volume = {39},
number = {1},
year = {2009},
pages = { 1195-1224},
language = {en},
url = {http://dml.mathdoc.fr/item/1248269777}
}
Filipin, Alan. On the Size of Sets in Which $xy + 4$ is Always a Square. Rocky Mountain J. Math., Tome 39 (2009) no. 1, pp. 1195-1224. http://gdmltest.u-ga.fr/item/1248269777/