@article{10_4153_CMB_1991_048_x,
     author = {Bell, H. E. and Klein, A. A.},
     title = {On {Rings} {With} {Engel} {Cycles}},
     journal = {Canadian mathematical bulletin},
     pages = {295--300},
     year = {1991},
     volume = {34},
     number = {3},
     doi = {10.4153/CMB-1991-048-x},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1991-048-x/}
}