@article{10_1017_S0017089500008223,
     author = {Chon, I. and Lawson, J. D.},
     title = {Attainable sets and one-parameter semigroups of sets},
     journal = {Glasgow mathematical journal},
     pages = {187--201},
     year = {1991},
     volume = {33},
     number = {2},
     doi = {10.1017/S0017089500008223},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089500008223/}
}