1. Bary, N.K., Stechkin, S.B.: Best approximation and differential properties of two conjugate functions. Trudy Mosk. Mat. Obs. 5, 483–522 (1956). (in Russian)
2. Bergh, J., Löfström, J.: Interpolation Spaces. Springer-Verlag (Berlin-Heidelberg, An Introduction (1976)
3. Bergh, J., Peetre, J.: On the spaces $$V_p$$ ($$04. P. L. Butzer and R. J. Nessel, Fourier Analysis and Approximation. Vol. 1, Academic Press (New York–London, 1971)
5. Gogoladze, L., Meskhia, R.: On the absolute convergence of trigonometric Fourier series. Proc. Razmadze Math. Inst. 141, 29–40 (2006)