Global aspect of the astronomical correction for levelling of high precision when considering the definition of levelling datum / Ove Simonsen agard conference proceedings Radar propagation in the arctic / [ed. by Jon Frihagen] Museum en onderwijs : 50 jaar Jan Cunen Museum / [samenst. publ. Gemeentelijk Museum Jan Cunen Centrum, Oss ; eindred. P. Hagenaars] 1st conference on the importance of women in the nato defence / Danish Atlantic Association Risö : the research establishment of the Danish Atomic Energy Commission