LOUHIVAARA, Ilppo Simo; SIMADER, Christian G. Über periodische Lösungen koerzitiver linearer partieller Differentialgleichungen. Annales Fennici Mathematici, [S. l.], v. 4, n. 1, p. 87–108, 1979. DOI: 10.5186/aasfm.1978-79.0410. Disponível em: https://afm.journal.fi/article/view/134340. Acesso em: 7 jan. 2026.