Rao Kameswara O., and Venkateswarlu P. “Groundwater Quality: Focus on Fluoride in Selected Villages of S.P.S.R. Nellore District, Andhra Pradesh, India”. International Journal of Research in Chemistry and Environment (IJRCE), vol. 2, no. 1, Dec. 2011, pp. 150-2, https://ijrce.org/index.php/ijrce/article/view/150.