@inbook {Bertola:MasslessdeSitter,
	title = {Massless scalar field in a two-dimensional de Sitter universe},
	booktitle = {Rigorous quantum field theory},
	series = {Progr. Math.},
	volume = {251},
	year = {2007},
	pages = {27{\textendash}38},
	publisher = {Birkh{\"a}user},
	organization = {Birkh{\"a}user},
	address = {Basel},
	author = {Marco Bertola and Corbetta, Francesco and Moschella, Ugo}
}
