Whittington, P., Klages, N., Crawford, R., Wolfaardt, A. and Kemper, J. 2005. Age at first breeding of the African Penguin. Ostrich: Journal of African Ornithology. 76, 1-2 (Apr. 2005), 14–20. DOI:https://doi.org/10.2989/00306520509485468.