Ohlen, C.; Aggarwal, R. K.: 'Digital communications and fibre optics' (Energy Engineering, 1995), 'Power System Protection 4: Digital protection and signalling', Chap. 3, pp. 40-57, DOI: 10.1049/PBPO905J_ch3
IET Digital Library, https://digital-library.theiet.org/;jsessionid=d42paoqqmjk9.x-iet-live-01content/books/10.1049/pbpo905j_ch3