ASKIN, MUZAFFER, et al. “1H NMR Study of Chiral Monoaza-15-Crown-5 Ether Derivative by Relaxation Time T1”. Asian Journal of Chemistry, vol. 20, no. 2, Mar. 2010, pp. 1323-7, https://asianpubs.org/index.php/ajchem/article/view/12544.