Hirokazu Anai Shinji Hara Masaaki Kanno Kazuhiro Yokoyama Parametric polynomial spectral factorization using the sum of roots and its application to a control design problem. 703-725 2009 44 J. Symb. Comput. 7 http://dx.doi.org/10.1016/j.jsc.2008.04.015 db/journals/jsc/jsc44.html#AnaiHKY09