@article{AIHPA_1998__68_1_17_0,
     author = {Petkov, Vesselin and Popov, Georgi},
     title = {Semi-classical trace formula and clustering of eigenvalues for {Schr\"odinger} operators},
     journal = {Annales de l'I.H.P. Physique th\'eorique},
     pages = {17--83},
     publisher = {Gauthier-Villars},
     volume = {68},
     number = {1},
     year = {1998},
     mrnumber = {1618918},
     zbl = {0919.35095},
     language = {en},
     url = {http://archive.numdam.org/item/AIHPA_1998__68_1_17_0/}
}