1. Sections 1–3. Theorem 3.1 is due to Simonenko I.B. Simonenko: Some general questions on the theory of the Riemann boundary problem. Izv. Akad. Nauk SSSRSer. Mat. 32 (1968), 1138–1146
2. Sections 1–3. Theorem 3.1 is due to Simonenko I.B. Simonenko: Some general questions on the theory of the Riemann boundary problem. Math USSR Izv. 2(1968), 1091–1099
3. also Widom H. Widom: Singular integral equations in L. Trans. Amer. Math. Soc. 97(1960), 131–160.
4. The method of proof used to obtain Theorem 3.1 follows Krupnik N. Ya. Krupnik: Some general basic theorems on one dimensional singular integral operators with matrix coefficients. MAT. Issled. 42(1976), 91–112.
5. (Russian)], In particular, Lemmas 3.1, 3.2 and the nice results in Propositions 3.1, 3.2, 3.3 are from Krupnik N. Ya. Krupnik: Some general basic theorems on one dimensional singular integral operators with matrix coefficients. MAT. Issled. 42(1976), 91–112. (Russian)]. The proof of Proposition 2.1 is adapted from Clancey