LAHTINEN, A. On the existence of singular solutions of Δu = Pu on Riemann surfaces. Annales Fennici Mathematici, [S. l.], n. 546, 1973. DOI: 10.5186/aasfm.1973.546. Disponível em: https://afm.journal.fi/article/view/134202. Acesso em: 11 apr. 2025.