MEASUREMENTS OF AIRBORNE RADIONUCLIDES 221 13. T. Hvinden, A. Lillegraven, and O. Lillesaeter, Seasonal and Latitudina Variations in Radioactive Fallout, Report F-412, Norwegian Defence Re- search Establishment, January 1961. 14, R-W, Perkins, Physical and Chemical Formsof !9'] from Fallout and Chem- ical Processing Plants,in Hanford Radiological Science Research and Development Annual Report for 1963, USAEC Report HW-81746, Hanford Atomic Products Operation, January 1964,