1. S. K. Pichorides, "On the best values of the constants in theorems of M. Riesz, Zygmund, and Kolmogorov," Studia Math.,44, No. 2, 165?179 (1972).
2. I. Ts. Gokhberg and N. Ya. Krupnik, "On the norm of the Hilbert transformation in an LP-space," Funktsional. Analiz i Ego Prilozhen.,2, No. 2, 91?92 (1968).
3. A. M. Sedletskii, "Equivalent sequences in some function spaces," Izv. VUZov, Matematika,134, No. 7, 85?91 (1973).