On the Constant in The Lower Estimate for the Bernstein Operator
  For functions belonging to the classes $C^{2}[0, 1]$ and $C^{3}[0, 1]$, we establish the lower estimate with an explicit constant in approximation by Bernstein polynomials in terms of the second order Ditzian-Totik modulus of smoothness. Several applications to some concrete examples of functions are presented. 
Sorin Gal and Gancho Tachev
math.CA