Hagen, O. A. (2010). Digital books: Competition and commerce. Nova Science Publishers.
芝加哥风格引文Hagen, Oliver A. Digital Books: Competition and Commerce. New York: Nova Science Publishers, 2010.
MLA引文Hagen, Oliver A. Digital Books: Competition and Commerce. Nova Science Publishers, 2010.
警告：这些引文格式不一定是100％准确.