@article{TAC_2004_12_a8,
     author = {Michel Hebert},
     title = {Algebraically closed and existentially closed substructures in 
categorical context},
     journal = {Theory and applications of categories},
     pages = {269--298},
     publisher = {mathdoc},
     volume = {12},
     year = {2004},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/TAC_2004_12_a8/}
}