A theorem of Korovkin states that a sequence of positive linear operators on C[ a, b] converges strongly to the identity if and only if convergence holds on a three-dimensional Chebyshev subspace of C ...

SIAM Journal on Numerical Analysis, Vol. 52, No. 4 (2014), pp. 1913-1927 (15 pages) Polynomial interpolants defined using Chebyshev extreme points as nodes converge uniformly at a geometric rate when ...