SINISALO, J. Engels brev: C. L. Engel. Kirjeet - Brev - Briefe 1813-1840, red Mikael Sundman. Historisk Tidskrift för Finland, [S. l.], v. 75, n. 3, 1990. Disponível em: https://journal.fi/htf/article/view/65444. Acesso em: 15 maj. 2024.