1. G. Grubb Distributions and Operators, Springer, New York, 2009.
2. L. Hörmander The Analysis of Linear Partial Differential Operators I. Distribution Theory and Fourier Analysis, Springer, Berlin, 1983.
3. A. V. Bitsadze, “On solution uniqueness of the Dirichlet problem for partial elliptic equations,” Uspekhi Mat. Nauk, 3, 211–212 (1948).
4. S. Albeverio, F. Gesztesy, R. Hoegh-Krohn, and H. Holden, Solvable Models in Quantum Mechanics, Springer, Berlin, 1988.
5. B. Brown, G. Grubb, and I. G. Wood, “M-functions for closed extensions of adjoint pairs of operators with applications to elliptic boundary problems,” Math. Nachr., 282, 314–347 (2009).