Letter from Gregory J Williams, Senior Research Aide, to Dr Gottfried Wiegand, Geographischen Instituts, Universitat Wurzburg, Wurzburg, Germany Asks for a copy of a photograph of a pingo in Greenland featured in Dr Wiegand's dissertation, 'Fossile pingos in Mitteleuropa'. Says that Gold has long held that many of the domes on the Moon are pingos and that some of the craters are collapsed pingos. 30 August 1967