TY  - JOUR
AU  - Zurab Janelidze
TI  - The pointed subobject functor, 3 x 3 lemmas, and subtractivity of spans
JO  - Theory and applications of categories
PY  - 2010
SP  - 221
EP  - 242
VL  - 23
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/TAC_2010_23_a10/
LA  - en
ID  - TAC_2010_23_a10
ER  -