@article{10_4153_CMB_1991_039_0,
     author = {Lowen-Colebunders, E. and Szabo, Z. G.},
     title = {Simplicity of {Categories} {Defined} by {Symmetry} {Axioms}},
     journal = {Canadian mathematical bulletin},
     pages = {240--248},
     year = {1991},
     volume = {34},
     number = {2},
     doi = {10.4153/CMB-1991-039-0},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1991-039-0/}
}