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S. P. Sidorov. Negative property of shape preserving finite-dimensional linear operators // Applied Mathematics Letters, Elsevier Science Ltd.. Vol. 16, № 2, 2003.
S. P. Sidorov. Approximation of the r-th differential operator by means of linear shape-preserving operators of finite rank // Journal of Approximation Theory, Elsevier Science Ltd.. Vol. 124, № 2, 2003.
S. P. Sidorov. On estimates of n-th minimal error of linear algorithms on some sets of dimension of n+1 // Global J. of Pure and Appl. Math. Vol. 1, № 1, 2005.