@incollection {MR1603219,
    AUTHOR = {Kawski, Matthias and Sussmann, H{\'e}ctor J.},
     TITLE = {Noncommutative power series and formal {L}ie-algebraic
              techniques in nonlinear control theory},
 BOOKTITLE = {Operators, systems, and linear algebra ({K}aiserslautern,
              1997)},
    SERIES = {European Consort. Math. Indust.},
     PAGES = {111--128},
 PUBLISHER = {Teubner},
   ADDRESS = {Stuttgart},
      YEAR = {1997},
   MRCLASS = {93B25 (34E05 34H05 93C10)},
  MRNUMBER = {MR1603219 (99a:93021)},
MRREVIEWER = {Andrey V. Sarychev},
}