JENSEN, O. R. Construction of vacuum for the positive-energy representation and its Bose counterpart. MATHEMATICA SCANDINAVICA, [S. l.], v. 80, p. 101–106, 1997. DOI: 10.7146/math.scand.a-12613. Disponível em: https://www.mscand.dk/article/view/12613. Acesso em: 6 may. 2024.