@article{ASENS_2003_4_36_1_1_0,
     author = {Colin de Verdi\`ere, Yves and V\~{u} Ngọc, San},
     title = {Singular {Bohr-Sommerfeld} rules for {2D} integrable systems},
     journal = {Annales scientifiques de l'\'Ecole Normale Sup\'erieure},
     pages = {1--55},
     publisher = {Elsevier},
     volume = {Ser. 4, 36},
     number = {1},
     year = {2003},
     doi = {10.1016/S0012-9593(03)00002-8},
     zbl = {1028.81026},
     language = {en},
     url = {http://www.numdam.org/articles/10.1016/S0012-9593(03)00002-8/}
}