1. [2] D. Barbasch and D. A. Vogan, Jr., The local structure of characters, J. Funct. Anal. 37 (1980), 27–55.
2. [4] J. M. Bony, “Équivalence des diverses notions de spectre singulier analytique” in Séminaire Goulaouic-Schwartz (1976/1977), Équations aux dérivées partielles et analyse fonctionnelle, Exp. No. 3, Centre Math., École Polytech., Palaiseau, 1977, 1–12.
3. [5] A. Cannas da Silva, Lecture on Symplectic Geometry, Lecture Notes in Math. 1764, Springer, Berlin, 2001.
4. [6] A. Córdoba and C. Fefferman, Wave packets and Fourier integral operators, Comm. Partial Differential Equations 3 (1978), 979–1005.
5. [7] J. Dixmier, $C^{*}$-Algebras, North-Holland Math. Library 15, North-Holland, Amsterdam, 1977.