Quetin-Leclercq, J., Tits, M., Angenot, M.-L., & Bisset, N. G. (1991). Alkaloids of Strychnos usambarensis Stem Bark. Planta Medica : natural products and medicinal plant research, 57(5), 501. https://doi.org/10.1055/s-2006-960185 (Original work published 1991)