@article{TAC_2006_16_a11,
     author = {Zurab Janelidze},
     title = {Closedness properties of internal relations {I:}  {A} unified approach {to
Mal'tsev,} unital and subtractive categories},
     journal = {Theory and applications of categories},
     pages = {236--261},
     publisher = {mathdoc},
     volume = {16},
     year = {2006},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/TAC_2006_16_a11/}
}