@article{IM2_2008_72_2_a1,
     author = {I. K. Babenko and S. A. Bogatyi},
     title = {On the group of substitutions of formal power series with integer coefficients},
     journal = {Izvestiya. Mathematics },
     pages = {241--264},
     publisher = {mathdoc},
     volume = {72},
     number = {2},
     year = {2008},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_2008_72_2_a1/}
}