GARRISON, Randy. Theoretical Challenges for Distance Education in the 21st Century: A Shift from Structural to Transactional Issues. The International Review of Research in Open and Distributed Learning, [S. l.], v. 1, n. 1, 2000. DOI: 10.19173/irrodl.v1i1.2. Disponível em: https://www.irrodl.org/index.php/irrodl/article/view/2. Acesso em: 19 apr. 2024.