Arendse, M. S., I. A. Dubery, and D. K. Berger. “Isolation by PCR-Based Methods of a Plant Antifungal Polygalacturonase-Inhibiting Protein Gene”. Electronic Journal of Biotechnology, vol. 2, no. 3, Dec. 1999, pp. 0-0, https://www.ejbiotechnology.info/index.php/ejbiotechnology/article/view/v2n3-4.