@article{10_4153_CMB_1994_050_4,
     author = {Dokovi\'c, D. \v{Z}. and Check, P. and H\'ee, J.-Y.},
     title = {On {Closed} {Subsets} of {Root} {Systems}},
     journal = {Canadian mathematical bulletin},
     pages = {338--345},
     year = {1994},
     volume = {37},
     number = {3},
     doi = {10.4153/CMB-1994-050-4},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1994-050-4/}
}