Sammut, R.A.: 'Discrete radiation from curved single-mode fibres', Electronics Letters, 1977, 13, (14), p. 418-419, DOI: 10.1049/el:19770304
IET Digital Library, https://digital-library.theiet.org/;jsessionid=123vum4dk9ch.x-iet-live-01content/journals/10.1049/el_19770304