1. T. Carleman, Ark. Mat., Astr. Fys. 26 (17), 1 (1939).
2. L. Hörmander, The Analysis of Linear Partial Differential Operators III. Pseudo-Differential Operators (Springer-Verlag, Berlin, 1987).
3. F. Treves, Introduction of Pseudodifferential and Fourier Integral Operators (Springer, New York, 1980).
4. V. V. Grushin and N. A. Shananin, Math. USSR-Sb. 32 (1), 32 (1977).
5. N. A. Shananin, Sb. Math. 191 (3), 431 (2000).