Approximation by bounded pseudo-polynomials
C. Cottin, in: Function Spaces, Proc. Conf. Poznan 1989, Teubner, 1991, pp. 152–161.

Global smoothness preservation by multivariate approximation operators
C. Anastassiou, C. Cottin, H. Gonska, in: S. Baron, D. Leviatan (Eds.), Israel Mathematical Conference Proceedings, Vol. IV, 1991, pp. 31–44.

Global smoothness of approximating functions
G.A. Anastassiou, C. Cottin, H.H. Gonska, Analysis 11 (1991).