A characterization of weighted approximations by the Post-Widder and the Gamma operators. - Borislav R. Draganov; Kamen G. Ivanov (J. Approx. Theory, 2007)

Exact estimates of the rate of approximation of convolution operators. - Borislav R. Draganov (J. Approx. Theory, 2010)

A characterization of weighted approximations by the Post-Widder and the Gamma operators, II. - Borislav R. Draganov; Kamen G. Ivanov (J. Approx. Theory, 2010)

Strong estimates of the weighted simultaneous approximation by the Bernstein and Kantorovich operators and their iterated Boolean sums. - Borislav R. Draganov (J. Approx. Theory, 2015)

Simultaneous approximation by Bernstein polynomials with integer coefficients. - Borislav R. Draganov (J. Approx. Theory, 2019)

Corrigendum to "Strong estimates of the weighted simultaneous approximation by the Bernstein and Kantorovich operators and their iterated Boolean sums" [J. Approx. Theory 200 (2015) 92-135]. - Borislav R. Draganov (J. Approx. Theory, 2020)

Direct estimates of the weighted simultaneous approximation by the Szász-Mirakjan operator. - Borislav R. Draganov (Period. Math. Hung., 2021)