JENSEN, Arne. Some remarks on eigenfunction expansions for Schrödinger operators with non-local potentials. Mathematica Scandinavica, Berkeley, CA, United States, v. 41, p. 347–357, 1977. DOI: 10.7146/math.scand.a-11727. Disponível em: https://journals.msp.org/mscand/article/view/1918. Acesso em: 25 jul. 2026.