@article{SM_1972_18_2_a6,
     author = {V. V. Konyukhovskii},
     title = {Some metric properties of {Engel's} representation},
     journal = {Sbornik. Mathematics},
     pages = {249--265},
     publisher = {mathdoc},
     volume = {18},
     number = {2},
     year = {1972},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1972_18_2_a6/}
}