Freris, L.L.; Sasson, A.M.: 'Investigation of the load-flow problem', Proceedings of the Institution of Electrical Engineers, 1968, 115, (10), p. 1459-1470, DOI: 10.1049/piee.1968.0260
IET Digital Library, https://digital-library.theiet.org/;jsessionid=9il8vl5l982a.x-iet-live-01content/journals/10.1049/piee.1968.0260