@article{TRSPY_2000_231_a0,
     author = {L. Bartholdi and R. I. Grigorchuk},
     title = {On the {Spectrum} of {Hecke} {Type} {Operators} {Related} to {Some} {Fractal} {Groups}},
     journal = {Informatics and Automation},
     pages = {5--45},
     publisher = {mathdoc},
     volume = {231},
     year = {2000},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/TRSPY_2000_231_a0/}
}