1. Alpay, D.: Some remarks on reproducing kernel Kreĭn spaces. Rocky Mountain J. Math. 21, 1189–1205 (1991)
2. Alpay, D.: The Schur algorithm, reproducing kernel spaces and system theory. American Mathematical Society, Providence, RI (2001) Translated from the 1998 French original by Stephen S. Wilson, Panoramas et Synthèses [Panoramas and Syntheses]
3. Alpay, D., Azizov, T.Ya., Dijksma, A., Rovnyak, J.: Colligations in Pontryagin spaces with a symmetric characteristic function. In: Linear operators and matrices, vol. 130 of Oper. Theory Adv. Appl., pp. 55–82. Birkhäuser, Basel (2002)
4. Alpay, D., Bolotnikov, V., Dijksma, A., De Snoo, H.: On some operator colligations and associated reproducing kernel Pontryagin spaces. J. Func. Anal. 136, 39–80 (1996)
5. Alpay, D., Bolotnikov, V., Loubaton, Ph.: Dissipative periodic systems and symmetric interpolation in Schur classes. Arch. Math. (Basel) 68, 371–387 (1997)