• [Wiki] https://en.wikipedia.org/wiki/Raja_undulata.
• [fishbase] https://www.fishbase.de/summary/Raja-undulata.html.
• [CoelErzi2002] Coelho, R. and Erzini, K. (2002). Age and growth of the undulate ray, Raja undulata, in the Algarve (southern Portugal). J. Mar. Biol. Ass. U.K., pages 987--990. doi:10.1071/MF18010.
• [Kooy2010] Kooijman, S. (2010). Dynamic Energy Budget theory for metabolic organisation. Cambridge Univ. Press, Cambridge.
• [SerrErzi2015] Serra-Pereira, B., Erzini, K., and Figueiredo, I. (2015). Using biological variables and reproductive strategy of the undulate ray Raja undulata to evaluate productivity and susceptibility to exploitation. J Fish Biol., pages 1471--90. doi:10.1111/jfb.12653.