@article{TAC_2006_17_a4,
     author = {Guo-Qiang Zhang and Gongqin Shen},
     title = {Approximable {Concepts,} {Chu} spaces, and  information systems},
     journal = {Theory and applications of categories},
     pages = {79--102},
     publisher = {mathdoc},
     volume = {17},
     year = {2006},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/TAC_2006_17_a4/}
}