Barlow, A.J.; Payne, D.N.; Hadley, M.R.; Mansfield, R.J.: 'Production of single-mode fibres with negligible intrinsic birefringence and polarisation mode dispersion', Electronics Letters, 1981, 17, (20), p. 725-726, DOI: 10.1049/el:19810509
IET Digital Library, https://digital-library.theiet.org/;jsessionid=411losofundl3.x-iet-live-01content/journals/10.1049/el_19810509