Farries, M.C.; Russell, P.ST.J.; Fermann, M.E.; Payne, D.N.: 'Second-harmonic generation in an optical fibre by self-written χ<sub>(2)</sub> grating', Electronics Letters, 1987, 23, (7), p. 322-324, DOI: 10.1049/el:19870239
IET Digital Library, https://digital-library.theiet.org/;jsessionid=p07om817mdfk.x-iet-live-01content/journals/10.1049/el_19870239