Diurnal and Seasonal Variation of Surface Refractivity in Minna and Lapai, North Central Nigeria. (2018). International Journal of Engineering Research and Advanced Technology (ijerat) (E-ISSN 2454-6135) DOI: 10.31695 IJERAT, 4(7), 16-24. https://doi.org/10.31695/IJERAT.2018.3283