Crawford, R., P. Sabarros, T. Fairweather, L. Underhill, and A. Wolfaardt. “Implications for Seabirds off South Africa of a Long-Term Change in the Distribution of Sardine”. African Journal of Marine Science, vol. 30, no. 1, June 2008, pp. 177-84, doi:10.2989/ajms.2008.30.1.18.468.