1. Pacific North-West Laboratory, The ${}^{3}He$ Supply Problem, available at
http://www.pnl.gov/main/publications/external/technical_reports/PNNL-18388.pdf
2. European Spallation Source, available at
http://europeanspallationsource.se/
3. O. Kirstein et al., PoS (Vertex2014), 029 (2014) arXiv:1411.6194
4. S. Peggs, European Spallation Source Technical Design Report, report 2013-0001, Esss.se
5. K. Kanaki et al., J. Instrum. 13, P07016 (2018)