@article {LieTic09,
    AUTHOR = {Liesen, J{\"o}rg and Tich{\'y}, Petr},
     TITLE = {On best approximations of polynomials in matrices in the matrix 2-norm},
   JOURNAL = {SIAM J. Matrix Anal. Appl.},
  FJOURNAL = {SIAM Journal on Matrix Analysis and Applications},
    VOLUME = {31},
      YEAR = {2009},
    NUMBER = {2},
     PAGES = {853--863},
}