@article{10_4153_CMB_2005_054_8,
     author = {Lopes, Samuel A.},
     title = {Separation of {Variables} for},
     journal = {Canadian mathematical bulletin},
     pages = {587--600},
     year = {2005},
     volume = {48},
     number = {4},
     doi = {10.4153/CMB-2005-054-8},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-2005-054-8/}
}