Fallout in the United States and other areas. July-December 1968 and January-December 1969.
D009656:North America; D011847:Radioactive Fallout / Q000032:analysis*; D013020:South America; D013325:Strontium Isotopes / Q000032:analysis*; D014481:United States
D011847:Radioactive Fallout; D013325:Strontium Isotopes