WALTER, Johann. Note on a Paper by Stetkær-Hansen Concerning Essential Selfadjointness of Schroedinger Operators. Mathematica Scandinavica, Berkeley, CA, United States, v. 25, p. 94–96, 1969. DOI: 10.7146/math.scand.a-10943. Disponível em: https://journals.msp.org/mscand/article/view/2397. Acesso em: 25 jul. 2026.