D. A. Longbottom, V. Franckevičius, and S. V. Ley, “(S)- and (R)-5-Pyrrolidin-2-yl-1H-tetrazoles: Enantiomeric Organocatalysts of Broad Utility in Organic Synthesis”, Chimia, vol. 61, no. 5, p. 247, May 2007.