1. Tsegaye G. Ayele, Sergey E. Mikhailov (2011), Analysis of two-operator boundary-domain integral equations for a variable-coefficient BVP, in: Eurasian Math. J.,
2:3 (2011), 20–41.
2. O. Chakuda, S.E. Mikhailov, D. Natroshvili, Analysis of direct boundary-domain integral equations for a mixed BVP with variable coefficient. I: Equivalence and Invertibility. J. Integral Equat. and Appl. 21 (2009), 499–543.
3. Constanda, C.: Direct and Indirect Boundary Integral Equation Methods. Chapman & Hall/CRC (2000).
4. Mikhailov, S.E.: Analysis of Segregated Boundary-Domain Integral Equations for variable coefficient Dirichlet and Neumann problems with general date. ArXiv:1509.03501, 1–32 (2015).
5. M. Costabel, Boundary integral operators on Lipchitz domains: elementary results. SIAM journal on Mathematical Analysis 19 (1988), 613–626.