LÖFSTRÖM, Jörgen. On Certain Interpolation Spaces Related to Generalized Semi-Groups. Mathematica Scandinavica, Berkeley, CA, United States, v. 16, p. 41–54, 1965. DOI: 10.7146/math.scand.a-10747. Disponível em: https://journals.msp.org/mscand/article/view/2574. Acesso em: 25 jul. 2026.