Gas Chromatography-Mass Spectrometry (GC-MS) Assay of Bio- Active Compounds and Phytochemical Analyses in Three Species of Apocynaceae, Willie, Peggy, Uyoh Edak A., and Aikpokpodion Peter O. , Pharmacognosy Journal, March 2021, Volume 13, Issue 2, p.383-392, (2021)