@article{10_4153_CMB_1972_055_0,
     author = {Herrlich, H. and Ringel, C. M.},
     title = {Identities in {Categories}},
     journal = {Canadian mathematical bulletin},
     pages = {297--299},
     year = {1972},
     volume = {15},
     number = {2},
     doi = {10.4153/CMB-1972-055-0},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1972-055-0/}
}