Akbar Ali Jilani, M. Ayub Khan Yousuf Zai, M. Ayub Khan Yousuf Zai, Faisal Ahmed Khan Afridi, Khusro Mian, Syed Nazeer Alam. (2013) Seasonal Variability in Virtual Height of Ionospheric F2 Layer at the Pakistan Atmospheric Region, , Volume 50, Issue 2.