Lunt, N.; Kersley, L.; Bailey, G.J.; Bishop, G.J.; Mazzella, A.J.: 'Effects of the protonosphere on GPS systems: modelling and observations', IET Conference Proceedings, 1999, p. 200-203, DOI: 10.1049/cp:19990050
IET Digital Library, https://digital-library.theiet.org/;jsessionid=3fkwihjwdj2e1.x-iet-live-01content/conferences/10.1049/cp_19990050