@article{SF_1989__39_2_134974,
     author = {H. Cohen},
     title = {Bands on trees.},
     journal = {Semigroup forum},
     pages = {59--64},
     publisher = {mathdoc},
     volume = {39},
     number = {2},
     year = {1989},
     zbl = {0681.22002},
     url = {http://geodesic.mathdoc.fr/item/SF_1989__39_2_134974/}
}