'Basic elements of digital protection' (Energy Engineering, 1995), 'Digital Protection for Power Systems', Chap. 3, pp. 39-59, DOI: 10.1049/PBPO015E_ch3
IET Digital Library, https://digital-library.theiet.org/;jsessionid=5e05go3a5wmus.x-iet-live-01content/books/10.1049/pbpo015e_ch3