# Bounding my Erdös number

From the definition of the Erdös number, to establish a bound of 4 for mine, it suffices to supply the following citations.
1. Anderson, J.M., Erdös, P., Pinkus, A, Shisha, Oved,
The closed linear span of $\{x^k-c_k\}_1^{\infty}$.
J. Approx. Theory 43 (1985), pp. 75--80.
2. Pinkus, A, Braess, D,
Interpolation by Ridge Functions,
J. Approx. Theory 73 (1993), pp. 218-236
3. Braess, D, C. Schwab,
Approximation on simplices with respect to weighted Sobolev norms.
J. Approx. Theory 103 (2001), No. 2, 329-337.
4. J.M. Melenk, C. Schwab,
Analytic regularity for a singularly perturbed problem,
SIAM J. Math. Anal. 30 (1999), 379-400