PETROV, V. V. Das biharmonische Integral von Poisson. Lithuanian Mathematical Journal, [S. l.], v. 7, n. 1, p. 137–142, 1967. DOI: 10.15388/LMJ.1967.19939. Disponível em: https://www.journals.vu.lt/LMJ/article/view/19939.. Acesso em: 6 may. 2024.