@article {planck2015XVIII,
	title = {Planck 2015 results. XVIII. Background geometry and topology of the Universe},
	journal = {\aap},
	volume = {594},
	year = {2016},
	month = {oct},
	pages = {A18},
	author = {\sorthelpPlanck Collaboration 201618Planck Collaboration and et al.}
}
