Varricchio, Sergio Luis; Freitas, Francisco Damasceno; Martins, Nelson: 'Hybrid modal-balanced truncation method based on power system transfer function energy concepts', IET Generation, Transmission & Distribution, 2015, 9, (11), p. 1186-1194, DOI: 10.1049/iet-gtd.2014.1116
IET Digital Library, http://digital-library.theiet.org/;jsessionid=jtdsfh7u9950.x-iet-live-01content/journals/10.1049/iet-gtd.2014.1116