Hanna, D.C.; Percival, R.M.; Perry, I.R.; Smart, R.G.; Suni, P.J.; Townsend, J.E.; Tropper, A.C.: 'Continuous-wave oscillation of a monomode ytterbium-doped fibre laser', Electronics Letters, 1988, 24, (17), p. 1111-1113, DOI: 10.1049/el:19880755 IET Digital Library, https://digital-library.theiet.org/;jsessionid=4s5ecqivrd78b.x-iet-live-01content/journals/10.1049/el_19880755