@article{JOLT_2002_12_2_a9,
     author = {M. H. Lee},
     title = {Casimir {Operators} on {Pseudodifferential} {Operators} of {Several} {Variables}},
     journal = {Journal of Lie Theory},
     pages = {483--493},
     year = {2002},
     volume = {12},
     number = {2},
     zbl = {1062.11025},
     url = {http://geodesic.mathdoc.fr/item/JOLT_2002_12_2_a9/}
}