@article{TAC_2001_8_a2,
     author = {J. Adamek and J. Rosicky},
     title = {On sifted colimits and generalized varieties},
     journal = {Theory and applications of categories},
     pages = {33--53},
     year = {2001},
     volume = {8},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/TAC_2001_8_a2/}
}