Anatoli Juditsky, Håkan Hjalmarsson, Albert Benveniste, Bernard Delyon, Lennart Ljung, Jonas SjÖberg, Qinghua Zhang,
Nonlinear black-box models in system identification: mathematical foundations Automatica. ,vol. 31, pp. 1725- 1750 ,(1995) ,
10.1016/0005-1098(95)00119-1