1. A.P. Bosznoy, A remark on simultaneous approximation, J. Approx. Theory 28 (1978), 296-298.
2. A.S. Holland, B.N. Sahney, and J.Tzimbalario, On best Simultaneous Approximation, J. Indian Math. Soc. 40 (1976), 69-73.
3. C. B. Dunham, Simultaneous Chebyshev Approximation of Functions on an Interval, Proc. Amer. Math. Soc.18 (1967), 472-477.
4. Chong Li, On Best Simultaneous Approximation, J. Approx. Theory 91, (1998) 332-348.
5. E. Abu-Sirhan, Best simultaneous approximation in L p I, X, Inter. J. Math. Analysis, vol. 3, no. 24, (2009) 1157-1168.