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2. Full committee hearing before the committee on energy and natural resources, United States Senate. The Helium Stewardship Act of 2012;
http://go.nature.com/C1xdA1
3. Full committee hearing before the committee on energy and natural resources, United States Senate. The Helium Stewardship Act of 2013;
http://go.nature.com/s7cwu2
4. The Helium Stewardship Act of 2013;
https://www.govtrack.us/congress/bills/113/hr527/text
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