“…, r. An open-ended arc L m in L is said to be closed if its endpoints are included in L m . By L we denote any closed part of L without the nodes c 1 In the following, we assume that the functions ϕ(t) and ψ(t) occurring in (1) and (2) belong to the class H * (L), and the coefficients a(t) and b(t) of the singular integral operator belong to the class H 0 (L). Moreover, a 2 (t) − b 2 (t) = 0 everywhere on L. For any interior point of L other than q, the singular integrals…”