Hult, Agneta, Ethel Dahlgren, David Hamilton, and Tor Söderström. “Teachers’ Invisible Presence in Net-Based Distance Education”. The International Review of Research in Open and Distributed Learning 6, no. 3 (February 22, 2006). Accessed April 28, 2024. https://www.irrodl.org/index.php/irrodl/article/view/262.