The 3-by-3 lemma for regular Goursat categories.
Lack, Stephen
Homology, Homotopy and Applications, Tome 6 (2004), p. 1-3 / Harvested from The Electronic Library of Mathematics
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Publié le : 2004-01-01
EUDML-ID : urn:eudml:doc:51584 
@article{02153099,
     title = {The 3-by-3 lemma for regular Goursat categories.},
     journal = {Homology, Homotopy and Applications},
     volume = {6},
     year = {2004},
     pages = {1-3},
     zbl = {1070.18007},
     language = {en},
     url = {http://dml.mathdoc.fr/item/02153099}
}

Lack, Stephen. The 3-by-3 lemma for regular Goursat categories.. Homology, Homotopy and Applications, Tome 6 (2004) pp. 1-3. http://gdmltest.u-ga.fr/item/02153099/