Katritzky, Alan R.; El-Mowafy, Azzahra M.; Musumarra, Giuseppe; Sakizadeh, Kumars; Sana-Ullah, Choudhry; et al. Journal of Organic Chemistry, 1981, vol. 46, # 19 p. 3823 - 3830 doi: 10.1021/jo00332a013