1. Contrexample in comonotone approximation of periodic functions;Dzyubenko;Trans. Inst. Math. NAS Ukraine,2008
2. Comonotone approximation of twice differentiable periodic functions;Dzyubenko;Ukrainian Math. J.,2009
3. Piecewise monotone pointwise approximation;Dzyubenko;Constr. approx.,1998
4. Uniform and pointwise shape preserving approximation by algebraic polynomials;Kopotun;Surv. Approx. Theory,2011
5. No Jackson-type estimates for piecewise q-monotone, q≥3, trigonometric approximation;Leviatan,2020