Potapov М., and Simonov Б. “Inequalities Refining Relationships Between Mixed Modules of Smoothness In Metrics of $L_p$ and $L_\infty$”. Bulletin of L.N. Gumilyov Eurasian National University. Mathematics, Computer Science, Mechanics Series, vol. 134, no. 1, Mar. 2021, pp. 19-34, doi:10.32523/2616-678X-2020-134-1-19-34.