Teijiro Isokawa Haruhiko Nishimura Naotake Kamiura Nobuyuki Matsui Associative Memory in quaternionic Hopfield Neural Network. 135-145 2008 18 Int. J. Neural Syst. 2 http://dx.doi.org/10.1142/S0129065708001440 db/journals/ijns/ijns18.html#IsokawaNKM08