1. Solvable Models in Quantum Mechanics;Albeverio,2005
2. Operational calculus of linear relations;Arens;Pac. J. Math.,1961
3. Bitangential Direct and Inverse Problems for Systems of Integral and Differential Equations;Arov,2012
4. Discrete and Continuous Boundary Problems;Atkinson,1964
5. Spectral theory for pairs of differential operators;Bennewitz;Ark. Mat.,1977