ON THE EQUIVALENCE OF THE K-FUNCTIONAL AND THE MODULUS OF CONTINUITY ON THE MORREY SPACES Статья Burenkov V., Ghorbanalizadeh A., Sawano Y. Journal of Approximation Theory. Том 248. 2019.
ON A PROBLEM OF OPTIMAL RECOVERY AND KOLMOGOROV TYPE INEQUALITIES ON AN INTERVAL Статья Bagramyan T.E. Journal of Approximation Theory. Том 189. 2015. С. 160-169
ESTIMATES FOR CONTINUITY ENVELOPES AND APPROXIMATION NUMBERS OF BESSEL POTENTIALS Статья Goldman M.L., Haroske D.D. Journal of Approximation Theory. Том 172. 2013. С. 58-85