A Lie group approach to steerable filters
@TechReport{michaelisTR94b,
  author = 	 "M. Michaelis and G. Sommer",
  title = 	 "A {L}ie group approach to steerable filters",
  institution =  "Inst. f. Inf. u. Prakt. Math.",
  year = 	 1994,
  number =       "9415",
  month =        "September",
  }