Norstog, Knut and Nicholls, Trevor J.. "3. Reproduction and Embryo Development". The Biology of the Cycads, Ithaca, NY: Cornell University Press, 1998, pp. 63-100. https://doi.org/10.7591/9781501737329-004
Norstog, K. & Nicholls, T. (1998). 3. Reproduction and Embryo Development. In The Biology of the Cycads (pp. 63-100). Ithaca, NY: Cornell University Press. https://doi.org/10.7591/9781501737329-004
Norstog, K. and Nicholls, T. 1998. 3. Reproduction and Embryo Development. The Biology of the Cycads. Ithaca, NY: Cornell University Press, pp. 63-100. https://doi.org/10.7591/9781501737329-004
Norstog, Knut and Nicholls, Trevor J.. "3. Reproduction and Embryo Development" In The Biology of the Cycads, 63-100. Ithaca, NY: Cornell University Press, 1998. https://doi.org/10.7591/9781501737329-004
Norstog K, Nicholls T. 3. Reproduction and Embryo Development. In: The Biology of the Cycads. Ithaca, NY: Cornell University Press; 1998. p.63-100. https://doi.org/10.7591/9781501737329-004