M. Yusoff, Siti Fairus, et al. “Protonated 14-Membered 5,5,7,12,12,14-Hexamethyl-1,4,8,11-Tetrazacyclotetradeca-7,14-Diene Salts and Their Biological Activity”. International Journal on Advanced Science, Engineering and Information Technology, vol. 3, no. 2, Apr. 2013, pp. 142-4, doi:10.18517/ijaseit.3.2.317.