@Article{AbrEriKoi09SP,
  author = 	 {T. Abrudan and J. Eriksson and V. Koivunen},
  title = 	 {Conjugate Gradient Algorithm for Optimization under Unitary Matrix Constraint},
  journal = 	 {Signal Processing (Elsevier)},
  year = 	 {2009},
  volume = 	 {89},
  number = 	 {9},
  pages = 	 {1704--1714},
  month = 	 {Sep.},
}