@article{10_4153_CJM_1971_088_4,
     author = {Lau, Anthony To-Ming},
     title = {Invariant {Means} on {Dense} {Subsemigroups} of {Topological} {Groups}},
     journal = {Canadian journal of mathematics},
     pages = {797--801},
     year = {1971},
     volume = {23},
     number = {5},
     doi = {10.4153/CJM-1971-088-4},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1971-088-4/}
}