@article{Kononovych_2008, title={Lower bound for the best approximations of periodic summable functions of two variables and their conjugates in terms of Fourier coefficients}, volume={60}, url={https://umj.imath.kiev.ua/index.php/umj/article/view/3222}, abstractNote={In terms of Fourier coefficients, we establish lower bounds for the sum of norms and the sum of the best approximations by trigonometric polynomials for functions from the space <i>L</i>(<i>Q</i>²) and functions conjugate to them with respect to each variable and with respect to both variables, provided that these functions are summable.}, number={8}, journal={Ukrains’kyi Matematychnyi Zhurnal}, author={Kononovych, T. O.}, year={2008}, month={Aug.}, pages={1042–1050} }