Maghanga , K. J., L. J. Kituyi, K. F. Segor, and O. P. Kisinyo. 2012. “Soil Phosphorous Extraction by Olsen and Double Acid Methods in Acid Soils of Western Kenya”. East African Journal of Pure and Applied Sciences 2 (1):Pg 1-5. http://ojs.uoeld.ac.ke/index.php/eapas/article/view/239.