Olaniyi, Oladimeji. “Mispronunciation of English Back Vowels Among Secondary School and Undergraduate Students in Lokoja, Kogi State, Nigeria”. Journal of Second and Multiple Language Acquisition-JSMULA (May 12, 2024): 446–467. Accessed May 15, 2024. https://science-res.com/index.php/jsmula/article/view/156.