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2. W. B. Gearhart, “Some Chebyshev Approximations by Polynomials in Two Variables,” J. Approx. Theory 8(3), 195–209 (1973).
3. N. N. Andreev and V. A. Yudin, “Polynomials of Least Deviation from Zero and Chebyshev-Type Cubature Formulas,” Tr. Mat. Inst. im. V.A. Steklova, Ross. Akad. Nauk 232, 45–57 (2001) [Proc. Steklov Inst. Math. 232, 39–51 (2001)].
4. M. Reimer, “Spherical Polynomial Approximations: A Survey,” in Advances in Multivariate Approximation, Ed. by W. Haussmann, K. Jetter, and M. Reimer (Wiley-VCH, Berlin, 1999), pp. 231–252.
5. S. N. Bernstein, Collected Works (Akad. Nauk SSSR, Moscow, 1952, 1954), Vols. 1, 2 [in Russian].