1. K. V. Runovskii and N. V. Omel’chenko, Mat. Zametki 100 (3), 421 (2016).
2. K. V. Runovskii and N. V. Omel’chenko, Math. Notes 100 (3), 448 (2016).
3. N. V. Omel’chenko, Mat. Zametki 103 (2), 319 (2018).
4. N. V. Omel’chenko, Math. Notes 103 (2), 312 (2018).
5. M. K. Potapov, B. V. Simonov, and S. Yu. Tikhonov, Fractional Moduli of Smoothness (Maks Press, Moscow, 2016) [in Russian].