SZALACH, A. J. Comparative analysis of selected market solutions for e-learning systems. Folia Toruniensia, [S. l.], v. 18, p. 171–185, 2018. DOI: 10.12775/FT.2018.009. Disponível em: https://apcz.umk.pl/FT/article/view/FT.2018.009. Acesso em: 16 jul. 2024.