@article {mcninch05:MR2142248,
    AUTHOR = {McNinch, George},
     TITLE = {Optimal ${\rm SL}(2)$ homomorphisms},
   JOURNAL = {Comment. Math. Helv.},
  FJOURNAL = {Commentarii Mathematici Helvetici. A Journal of the
                  Swiss
              Mathematical Society},
    VOLUME = 80,
      YEAR = 2005,
    NUMBER = 2,
     PAGES = {391--426},
      OPTISSN = {0010-2571},
   MRCLASS = {20G15 (14L24 14L30 20E45)},
  optMRNUMBER = {2142248 (2006f:20055)},
MRREVIEWER = {Guy Rousseau},
       OPTDOI = {10.4171/CMH/19},
       OPTURL = {http://dx.doi.org/10.4171/CMH/19},
}