“Diurnal and Seasonal Variation of Surface Refractivity in Minna and Lapai, North Central Nigeria”. International Journal of Engineering Research and Advanced Technology (ijerat) (E-ISSN 2454-6135) DOI: 10.31695 IJERAT, vol. 4, no. 7, July 2018, pp. 16-24, https://doi.org/10.31695/IJERAT.2018.3283.