Crush, J.R., H.S. Easton, and J.E. Waller. “Genetic Variation in Perennial Ryegrass for Root Profile Characteristics”. NZGA: Research and Practice Series 12 (January 1, 2006): 63–65. Accessed August 25, 2026. https://www.nzgajournal.org.nz/index.php/rps/article/view/3040.