HARPER, Joe G. A Conceptual Model for Developing Power and Machinery Instruction for Secondary Schools. Journal of Agricultural Systems, Technology, and Management, [S. l.], v. 5, n. 2, p. 16–23, 1990. Disponível em: https://jastm.org/index.php/jastm/article/view/11929. Acesso em: 23 feb. 2025.