Gosling, W.; Cunningham, M.J.: 'Gapped solenoid as a means of producing a highly uniform magnetic field over an extended volume', Proceedings of the Institution of Electrical Engineers, 1974, 121, (12), p. 1589-1593, DOI: 10.1049/piee.1974.0329
IET Digital Library, https://digital-library.theiet.org/;jsessionid=7dvahwb07eo.x-iet-live-01content/journals/10.1049/piee.1974.0329