“On the Variety of Auxinic Activity of Indol-03-Acetic, 4,5-Benzoindol-03-Acetic and 4,5-Naphthoindol-03-Acetic Acids”. Revista Española De Fisiología, vol. 15, no. 3, Sept. 1959, pp. 179-87, https://revistas.unav.edu/index.php/ref/article/view/48910.