LAHTINEN, A. On P-solvable functions for Δu = Pu on open Riemann surfaces. Annales Fennici Mathematici, [S. l.], n. 583, 1975. DOI: 10.5186/aasfm.1975.583. Disponível em: https://afm.journal.fi/article/view/134219. Acesso em: 25 nov. 2024.