Ditzian, Z. and Prymak, A. (2011). Extension technique and estimates for moduli of smoothness on domains in Rd. East J. Approx. 17 (2), 171–179.
Kopotun, K. A.; Leviatan, D.; Prymak, A. and Shevchuk, I. A. (2011). Uniform and pointwise shape preserving approximation by algebraic polynomials. Surv. Approx. Theory 6, 24–74.
Primak, A. V. (2005). Shape-preserving smoothing of 3-convex splines of degree four. Ukraı̈n. Mat. Zh. 57 (2), 277–283.
Bondarenko, Andriy V. and Prymak, Andriy V.. Convex multivariate approximation by algebras of continuous functions. In Advances in constructive approximation: Vanderbilt 2003 123–131. Nashboro Press, Brentwood, TN, 2004.
Ditzian, Z. and Prymak, A. (2011). Extension technique and estimates for moduli of smoothness on domains in Rd. East J. Approx. 17 (2), 171–179.
Kopotun, K. A.; Leviatan, D.; Prymak, A. and Shevchuk, I. A. (2011). Uniform and pointwise shape preserving approximation by algebraic polynomials. Surv. Approx. Theory 6, 24–74.
Primak, A. V. (2005). Shape-preserving smoothing of 3-convex splines of degree four. Ukraı̈n. Mat. Zh. 57 (2), 277–283.
Bondarenko, Andriy V. and Prymak, Andriy V.. Convex multivariate approximation by algebras of continuous functions. In Advances in constructive approximation: Vanderbilt 2003 123–131. Nashboro Press, Brentwood, TN, 2004.