@article{IM_1967__4_141891,
     author = {J. MENNICKE},
     title = {On {IHARA'S} {Modular} {Group.}},
     journal = {Inventiones mathematicae},
     pages = {202--228},
     publisher = {mathdoc},
     volume = {4},
     year = {1967},
     url = {http://geodesic.mathdoc.fr/item/IM_1967__4_141891/}
}