'Differential equation based techniques' (Energy Engineering, 1995), 'Digital Protection for Power Systems', Chap. 7, pp. 103-114, DOI: 10.1049/PBPO015E_ch7
IET Digital Library, https://digital-library.theiet.org/;jsessionid=15dhpbtiiot9i.x-iet-live-01content/books/10.1049/pbpo015e_ch7