@article {MR2578340,
    AUTHOR = {Feng, Ruyong and Singer, Michael F. and Wu, Min},
     TITLE = {Liouvillian solutions of linear difference-differential
              equations},
   JOURNAL = {J. Symbolic Comput.},
  FJOURNAL = {Journal of Symbolic Computation},
    VOLUME = {45},
      YEAR = {2010},
    NUMBER = {3},
     PAGES = {287--305},
      ISSN = {0747-7171},
   MRCLASS = {12H20 (12H05 34A30 39B42)},
  MRNUMBER = {2578340 (2010j:12011)},
MRREVIEWER = {I. S. Krasil{\cprime}shchik},
       DOI = {10.1016/j.jsc.2009.09.001},
       URL = {http://dx.doi.org/10.1016/j.jsc.2009.09.001},
}