@article{10_4153_CJM_1968_117_x,
     author = {JR., Kenneth D. Magill},
     title = {Restrictive {Semigroups} of {Closed} {Functions}},
     journal = {Canadian journal of mathematics},
     pages = {1215--1229},
     year = {1968},
     volume = {20},
     number = {1},
     doi = {10.4153/CJM-1968-117-x},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1968-117-x/}
}