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3. A. S. Belov, “On extremal problems on the set of nonnegative trigonometric polynomials,” in: Contemporary Problems of Function Theory and Its Applications. 12th Saratov Winter Workshop (27 Jan. – 3 Feb., 2004 ), [in Russian], GosUNC Kolledzh, Saratov (2004), pp. 19–21.
4. A. S. Belov, “On one sequence of nonnegative trigonometric polynomials,” Vestn. Ivanov. Univ., Ser. Biology, Chemistry, Physics, Mathematics, Vyp. 2, 104–114 (2011).
5. A. S. Belov, “On localization of zeros of some trigonometric polynomials,” Vestn. Ivanov. Univ., Ser. Biology, Chemistry, Physics, Mathematics, Vyp. 2, 92–106 (2012).