1. N.K. Bary, A Treatise on Trigonometric Series (MacMillan, New York, 1964)
2. O.V. Besov, V.P. Il’in, S.M. Nikol’skii, Integral Representation of Function and Imbedding Theorems (Wiley, New York, 1978/1979; translated from Russian: Nauka, Moscow, 1975)
3. M.K. Potapov, On “angular” Approximation, Proc. Conf. Constructive Functions Theory (Budapest, 1969) (Acad. Kiado, Budapest, 1971), pp. 371–399
4. M.K. Potapov, About one imbedding theorem. Mathematica (Clui) 14(37), 123–146 (1972)
5. M.K. Potapov, Imbedding of classes of function with a dominating mixed modulus of smoothness. Trudy Mat. Inst. Steklov. 131, 199–210 (1974)