Akgün, R. “Trigonometric Approximation of Functions in Generalized Lebesgue Spaces With Variable Exponent”. Ukrains’kyi Matematychnyi Zhurnal, vol. 63, no. 1, Jan. 2011, pp. 3-23, https://umj.imath.kiev.ua/index.php/umj/article/view/2695.