B. Helffer, Introduction to the semiclassical analysis for the Schrödinger operator and applications, p.1336, 1988.

B. Helffer and D. Robert, Comportement semi-classique du spectre des hamiltoniens quantiques hypoelliptiques, Annales ENS Pise IV, vol.9, issue.3, pp.405-431, 1982.

B. Helffer and J. Sjoestrand, Multiple wells in the semi-classical limit I, Communications in Partial Differential Equations, vol.52, issue.2, pp.337-408, 1984.
DOI : 10.1080/03605308408820335

B. Helffer and J. Sjoestrand, Puits multiples en mecanique semi-classique. VI, Ann. Institut H. Poincaré, Phys. Theor, vol.46, issue.4, pp.353-372, 1987.

L. Hörmander, The weyl calculus of pseudo-differential operators, Communications on Pure and Applied Mathematics, vol.111, issue.3, pp.359-443, 1979.
DOI : 10.1002/cpa.3160320304

V. Ivrii, Microlocal analysis and precise spectral asymptotic, 1998.
DOI : 10.1007/978-3-662-12496-3

B. M. Levitan, On the asymptotic behavior of Green's function and its expansion in eigenvalues of Schrödinger's equation, Math.USSR-Sb, pp.41-83, 1957.

A. G. Kostjucenko, Asymptotic distribution of the eigenvalues of elliptic operators, Soviet Math.Dokl, vol.5, pp.1171-1175, 1964.

A. Martinez, Développement asymptotiques et effet tunnel dans l'approximation de Born-Oppenheimer, Ann. Inst. Henri Poincaré, vol.49, issue.3, pp.239-257, 1989.
DOI : 10.5802/jedp.354

A. Morame and F. Truc, Semiclassical Eigenvalue Asymptotics for a Schrödinger Operator with Degenerate Potential, Asymptotic Anal, vol.22, issue.1, pp.39-49, 2000.

A. Morame and F. Truc, Accuracy on eigenvalues for a Schrödinger Operator with a Degenerate Potential in the semi-classical limit, Cubo, A Journal of Mathematics, vol.9, issue.2, pp.1-14, 2007.

M. Reed and B. Simon, Methods of Modern Mathematical Physics IV, Academic press, 1978.

D. Robert, Comportement asymptotique des valeurs propres d'opérateurs du type de SchrödingerSchrödingerà potentiel dégénéré, J.Math.Pures Appl, vol.61, pp.275-300, 1982.

G. V. Rosenbljum, ASYMPTOTICS OF THE EIGENVALUES OF THE SCHR??DINGER OPERATOR, Mathematics of the USSR-Sbornik, vol.22, issue.3, pp.349-371, 1974.
DOI : 10.1070/SM1974v022n03ABEH002167

M. A. Shubin, Pseudodifferential operators and spectral theory, 1987.
DOI : 10.1007/978-3-642-56579-3

B. Simon, Nonclassical eigenvalue asymptotics, Journal of Functional Analysis, vol.53, issue.1, pp.84-98, 1983.
DOI : 10.1016/0022-1236(83)90047-2

URL : http://doi.org/10.1016/0022-1236(83)90047-2

B. Simon, Semi-classical analysis of low lying eigenvalues I, Ann. Inst. H. Poincaré, vol.38, pp.295-307, 1983.

M. Z. Solomyak, ASYMPTOTICS OF THE SPECTRUM OF THE SCHR??DINGER OPERATOR WITH NONREGULAR HOMOGENEOUS POTENTIAL, Mathematics of the USSR-Sbornik, vol.55, issue.1, pp.19-37, 1986.
DOI : 10.1070/SM1986v055n01ABEH002989

E. C. Titchmarsh, ON THE ASYMPTOTIC DISTRIBUTION OF EIGENVALUES, The Quarterly Journal of Mathematics, vol.5, issue.1, pp.5-228, 1954.
DOI : 10.1093/qmath/5.1.228