SIMPSON, O. (2003). Student retention in online, open and distance learning. Kogan page.
芝加哥风格引文SIMPSON, Ormond. Student Retention in Online, Open and Distance Learning. Kogan page, 2003.
MLA引文SIMPSON, Ormond. Student Retention in Online, Open and Distance Learning. Kogan page, 2003.
警告：这些引文格式不一定是100％准确.