Mulchande, J. ., Martins, L. ., Moreira, R. ., Archer, M. ., Oliveira, T. ., & Iley, J. . (1969). The efficiency of C-4 substituents in activating the beta-lactam scaffold towards serine proteases and hydroxide ion. Organic & Biomolecular Chemistry, 5(16), 2617-26. (Original work published)