@article{RSMUP_2001__105__215_0,
     author = {Nicola, F.},
     title = {Weyl formula for quasi-elliptic pseudo-differential operators},
     journal = {Rendiconti del Seminario Matematico della Universit\`a di Padova},
     pages = {215--231},
     publisher = {Seminario Matematico of the University of Padua},
     volume = {105},
     year = {2001},
     mrnumber = {1834992},
     zbl = {1072.58018},
     language = {en},
     url = {http://archive.numdam.org/item/RSMUP_2001__105__215_0/}
}