@incollection {MR1493017,
    AUTHOR = {Kawski, Matthias},
     TITLE = {Nonlinear control and combinatorics of words},
 BOOKTITLE = {Geometry of feedback and optimal control},
    SERIES = {Monogr. Textbooks Pure Appl. Math.},
    VOLUME = {207},
     PAGES = {305--346},
 PUBLISHER = {Dekker},
   ADDRESS = {New York},
      YEAR = {1998},
   MRCLASS = {93C10 (93B29)},
  MRNUMBER = {MR1493017},
}