Rizk, F. (n.d). MARINE ENVIRONMENT AND PRIMARY PRODUCTIVITY. Available: "Primary Productivity". Archived from the original on 9 November 2014. Retrieved 15 May 2014.. Last accessed 15 May 2014.
Rizk, F. (n.d). MARINE ENVIRONMENT AND PRIMARY PRODUCTIVITY. Available: "Primary Productivity". Archived from the original on 9 November 2014. Retrieved 15 May 2014.. Last accessed 15 May 2014.