JENSEN, Ole Rask. Construction of vacuum for the positive-energy representation and its Bose counterpart. Mathematica Scandinavica, Berkeley, CA, United States, v. 80, p. 101–106, 1997. DOI: 10.7146/math.scand.a-12613. Disponível em: https://journals.msp.org/mscand/article/view/1013. Acesso em: 25 jul. 2026.