RYGAŁ, G. Long-term projects at school. Annales Universitatis Paedagogicae Cracoviensis Studia Mathematica, [S. l.], v. 3, p. 223–226, 2003. Disponível em: https://studmath.uken.krakow.pl/article/view/13492. Acesso em: 30 oct. 2026.