@article{SF_1990__41_2_135052,
     author = {J.D. Lawson and I. Chon},
     title = {Problems on semigroups and control.},
     journal = {Semigroup forum},
     pages = {245--252},
     publisher = {mathdoc},
     volume = {41},
     number = {2},
     year = {1990},
     zbl = {0707.93004},
     url = {http://geodesic.mathdoc.fr/item/SF_1990__41_2_135052/}
}