Aliyu, S., Garba, M.M., and Bande, A.B. “Effect of Height Variation for the Determination of Accurate Focal Zone for a Thin Foil L-Shaped Parabolic Reflector”. International Journal of Science for Global Sustainability, vol. 4, no. 2, Dec. 2017, p. 5, https://www.fugus-ijsgs.com.ng/index.php/ijsgs/article/view/168.