@article {Diamandis:1992sr,
	title = {{Does sigma model conformal invariance imply a Robertson-Walker universe?}},
	journal = {Phys. Lett. B},
	volume = {287},
	year = {1992},
	pages = {69{\textendash}72},
	doi = {10.1016/0370-2693(92)91878-D},
	author = {Diamandis, G. A. and Georgalas, B. C. and Lahanas, A.B.}
}
