[1] Járai, A.: Measurable solutions of functional equations satisfied almost everywhere. Math. Pannon. 10 (1999), 103-110. MR 1678112

[2] Krantz, S.: A Panorama of Harmonic Analysis, The Carus Mathematical Monographs. Number 27, The Mathematical Association of America, Washington D.C. (1999). MR 1710388

[3] Rudin, W.: Real and Complex Analysis. McGraw-Hill, New York, 1st edition (1966). MR 0210528 | Zbl 0142.01701

[4] Stein, E. M., Shakarchi, R.: Real Analysis. Princeton University Press, Princeton, New Jersey (2005). MR 2129625 | Zbl 1081.28001