@article{RCM_1993__27_1-2_181891,
     author = {R. M. S. Mahmud},
     title = {On commuting elemts of groups acting on trees},
     journal = {Revista colombiana de matematicas},
     pages = {293--301},
     publisher = {mathdoc},
     volume = {27},
     number = {1-2},
     year = {1993},
     zbl = {0813.20025},
     url = {http://geodesic.mathdoc.fr/item/RCM_1993__27_1-2_181891/}
}