On waves in the upper atmosphere / Hendrikus KelderMedium scale irregularities in the ionospheric electron content / Petrus Franciscus Johannes van VelthovenProblems of atmospheric and space electricity : proceedings of the third international conference on atmospheric and space electricity held at Montreux, Switzerland, May 5-10, 1963 / ed. by Samuel C. CoronitiTomography of the ionosphere / Gijsbert Christiaan FehmersExcitation mechanisms of medium scale travelling ionospheric disturbances / Herbert Samuël KoekkoekURSI handbook of ionogram interpretation and reduction of the World Wide Soundings Committee / ed. by W.R. Piggott and K. RawerWinds and turbulence in stratosphere, mesosphere and ionosphere : Proceedings of the NATO Advanced Study Institute, Lindau, Federal Republic of Germany, 18 Sept.-1 Oct. 1966 / ed. by K. RawerElectron density distribution in ionosphere and exosphere : proceedings of the NATO Advanced Study Institute, Skeikampen, Norway, 17-26 April 1963 / ed. by E. ThraneUpper air data and special synoptic observations / Koninklijk Nederlandsch Meteorologisch InstituutErgebnisse aerologischer Beobachtungen / Koninklijk Nederlandsch Meteorologisch InstituutSynoptic and upper air observations in the Netherlands / Koninklijk Nederlands Meteorologisch InstituutElectron density profiles in ionosphere and exosphere : proceedings of the NATO Advanced Study Institute, held at Finse, Norway, April 1965 / ed. by Jon Frihagen ; org. by the Norwegian Defense Research Establishment