Analysis of bioactive constituents of n-hexane and methanol fractions of Vernonia calvoana Extracts using Gas Chromatography- Mass Spectrometry, Iwara, Iwara A., Igile Godwin O., Uboh Friday E., Eteng Mbeh U., and Ebong Patrick.E. , Pharmacognosy Journal, August 2018, Volume 10, Issue 5, p.854-858, (2018)