1. Alexits, György, Convergence Problems of Orthogonal Series, International Series of Monographs on Pure and Applied Mathematics, Vol. 20. Pergamon Press (New York-Oxford-Paris, 1961).
2. Haar, Alfréd, Összegyűjtött Munkái = Gesammelte Arbeiten, ed. Béla Sz.-Nagy, Akadémiai Kiadó (Budapest, 1959).
3. [66]Hardy, G. H.-Riesz, Marcel, The General Theory of Dirichlet Series, Cambridge Tracts in Mathematics and Mathematical Physics, No. 18, Cambridge, University Press (London, 1915), reprint: 1952.
4. Hardy, G. H, Divergent Series, Oxford University Press (London, 1949).
5. Leindler, László, Strong Approximation by Fourier Series, Akadémiai Kiadó (Budapest, 1985).