@incollection{tretkoff:1984:cgt,
    author = {Tretkoff, C. L. and Tretkoff, M. D.},
     title = {Combinatorial Group Theory, {R}iemann Surfaces and
              Differential Equations},
 booktitle = {Contributions to Group Theory},
    series = {Contemp. Math.},
    volume = {33},
     pages = {467–519},
 publisher = {Amer. Math. Soc.},
   address = {Providence, RI},
      year = {1984},
   mrclass = {30F10 (12H05 20D60 20G20 22E40 34A99)},
  mrnumber = {MR0767125 (86g:30055)},
mrreviewer = {William Harvey},
     zblno = {0557.30036}}