M. U. Ali, M. Z. Haque, M. A. A. Maruf, and M. A. A.-. Sakia, “Mass Fragmentation Pattern of Some Mono- and Di-Substituted Formamidines. Part-1. Mass Pattern of 1-Arylformamidines”, Pakistan Journal of Scientific & Industrial Research, vol. 48, no. 6, pp. 386–388, Dec. 2005.