@article{10_4153_CMB_1974_045_5,
     author = {Lallement, Gerard},
     title = {On {Free} {Semigroups} and {Ramsey} {Numbers}},
     journal = {Canadian mathematical bulletin},
     pages = {229--232},
     year = {1974},
     volume = {17},
     number = {2},
     doi = {10.4153/CMB-1974-045-5},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1974-045-5/}
}