@article{AL_1998_37_6_a0,
     author = {P. de la Harpe and R. I. Grigorchuk},
     title = {Local convexity of growth functions of finitely generated},
     journal = {Algebra i logika},
     pages = {621--626},
     publisher = {mathdoc},
     volume = {37},
     number = {6},
     year = {1998},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1998_37_6_a0/}
}