Tomlinson, M.; Methiwalla, A.E.: 'Good performance i.f. and premodulation filters for simple f.s.k. system', Electronics Letters, 1973, 9, (26), p. 620-621, DOI: 10.1049/el:19730457
IET Digital Library, https://digital-library.theiet.org/;jsessionid=6qo04kbnf10id.x-iet-live-01content/journals/10.1049/el_19730457