@article{10_4064_fm_50_4_341_346,
     author = {R. Koch and L. McAuley},
     title = {Semigroups on trees},
     journal = {Fundamenta Mathematicae},
     pages = {341--346},
     publisher = {mathdoc},
     volume = {50},
     number = {4},
     year = {1961},
     doi = {10.4064/fm-50-4-341-346},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm-50-4-341-346/}
}