@article{ELMA_1955__10_140630,
     author = {J.-P. Sydler},
     title = {Le triangle comme op\'erateur g\'eom\'etrique.},
     journal = {Elemente der Mathematik},
     pages = {100--105},
     year = {1955},
     volume = {10},
     zbl = {0064.40001},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1955__10_140630/}
}