A. E. Ochoa-Alfaro, C. O. Silva-Ortega, A. Becerra-Flora, J. Flores-Rivas, and J. F. Jiménez-Bremont, “Effect of Salt Stress, Proline, and Polyamines on Seed Germination of Opuntia streptacantha”, J PROF ASSOC CACTUS, vol. 10, pp. 56–70, Jul. 2008.