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2. Weaknesses in DOE's Management of Helium-3 Delayed the Federal Response to a Critical Supply Shortage, Report to Congressional Requesters (United States Government Accountability Office, Library of Congress, 2011).
3. T. Feder, Phys. Today 62, 21 (2009).
4. J. Gillo, The Isotope Program fills critical needs for 3He in the United States. An earlier shortage has been mitigated, National Isotope Development Center Newsletter, March 2014.