@article{TAC_2014_29_a10,
     author = {Zurab Janelidze and Thomas Weighill},
     title = {Duality in non-abelian algebra {I.} {From} cover relations to {Grandis} 
ex2-categories},
     journal = {Theory and applications of categories},
     pages = {315--331},
     publisher = {mathdoc},
     volume = {29},
     year = {2014},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/TAC_2014_29_a10/}
}