@article{10_4153_CMB_1976_034_2,
     author = {Vranch, J.},
     title = {On {Critical} r, {\ensuremath{\lambda}-Systems}},
     journal = {Canadian mathematical bulletin},
     pages = {217--220},
     year = {1976},
     volume = {19},
     number = {2},
     doi = {10.4153/CMB-1976-034-2},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1976-034-2/}
}