@article{RM_1985_40_4_a12,
     author = {K. Tandori},
     title = {On sign systems},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {115--119},
     publisher = {mathdoc},
     volume = {40},
     number = {4},
     year = {1985},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/RM_1985_40_4_a12/}
}