STETKAER-HANSEN, Henrik. A Generalization of a Theorem of Wienholtz Concerning Essential Selfadjointness of Singular Elliptic Operators. Mathematica Scandinavica, Berkeley, CA, United States, v. 19, p. 108–112, 1966. DOI: 10.7146/math.scand.a-10798. Disponível em: https://journals.msp.org/mscand/article/view/2542. Acesso em: 25 jul. 2026.