O'Brien D.M. Geophysical distributions of occultations of GPS satellites viewed from a low earth orbiting satellite / D.M.O'Brien,P.Tregoning, 1998. - 31 p. - Текст : непосредственный.
Dynamic planet : monitoring and understanding a dynamic planet with geodetic and oceanographic tools IAG symposium, Cairns, Australia, 22 - 26 August, 2005 / ed. P. Tregoning, 2007 r=on-line. - Текст : электронный.