Mellor, P.H.; Leigh, S.P.; Cheetham, B.M.G.: 'Digital sampling process for audio class D, pulse width modulated, power amplifiers', Electronics Letters, 1992, 28, (1), p. 56-58, DOI: 10.1049/el:19920035
IET Digital Library, https://digital-library.theiet.org/;jsessionid=odc98aim08iv.x-iet-live-01content/journals/10.1049/el_19920035