1. Hasson, M. Comparison Between the Degree of Approximation by Lacunary and Ordinary Algebraic Polynomials. J. Approx. Theory 29(1980), 103–115.
2. Yang, Chengmin, A Counterexample to a Conjecture of Hasson. J. Approx. Theory 56(1989), 330–332.
3. Natanson, I.P. “Constructive Function Theory” Vol.1 Unger New York 1964.
4. Lorentz, G. G. Approximation by Incomplete polynomials (problem and results) in “Pade and Rational Approximation: Theory and Application” pp. 259–302. Academic Press, New York 1977.
5. Lorentz, G.G. “Approximation of Function” Holt Rinehart and Winston. Inc. 1966.