Dolgushev, Sergey Viktorovich, and Vasiliy Mikhaylovich Fomin. “Cyclic Helium Enrichment of Natural Gas in a Column With Glass Microspheres”. Computational Continuum Mechanics, vol. 1, no. 4, Apr. 2008, pp. 39-42, https://doi.org/10.7242/1999-6691/2008.1.4.36.