LAHTINEN, A. On the solutions of Δu = Pu for acceptable densities on open Riemann surfaces. Annales Fennici Mathematici, [S. l.], n. 515, 1972. DOI: 10.5186/aasfm.1972.515. Disponível em: https://afm.journal.fi/article/view/134171. Acesso em: 26 nov. 2024.