Urquhart, R.B.: 'Algorithms for computation of relative neighbourhood graph', Electronics Letters, 1980, 16, (14), p. 556-557, DOI: 10.1049/el:19800386
IET Digital Library, https://digital-library.theiet.org/;jsessionid=1vw7srttc7yfl.x-iet-live-01content/journals/10.1049/el_19800386