1. Shi Ying-guang, Uniform Approximation by Generalized Polynomials Having Bounded Coefficients,Acta Math. Appl. Sinica,5 (1982), 353–356.
2. Roulier, J. A., & Taylar, G. D., Uniform Approximation by Polynomials Having Bounded Coefficients,Abh. Math. Sem. Univ. Hamburg,36 (1971), 126–135.
3. Karlin, S., & Studden, W. J., Tchebycheff Systems: with Applications in Analysis and Statistics, Interscience, New York, 1966.
4. Passow, E., Polynomials with Positive Coefficients: Uniqueness of Best Approximation,J. Approx. Theory,21 (1977), 352–355.
5. Cheney, E. W., Introduction to Approximation Theory, McGraw-Hill, New York, 1966.