1. Helium shortage affecting instrument users to extend into 2013;Reisch;Chemical and Engineering News,2012
2. Helium headache;Widener;Chemical and Engineering News,2013
3. Helium shortage hampers research and industry;Kaplan;Physics Today,2007
4. Gabal, M. , Lozano, M.P., Oca, A., Pina, M.P., Sesé, J., Rillo, C. Helium contamination through plastic walls. 25th International Cryogenic Engineering Conference and the International Cryogenic Materials Conference in 2014, ICEC 25–ICMC 2014, University of Twente, Enschede, The Nederlands.
5. Rillo, C., and Sese, J., 2012. Medium Pressure Helium Recovery Plant (MP-HRP)Operating at University of Zaragoza. Product brochure from http://www.qdusa.com/products/helium-liquefiers.html.