Onward Tickets from Luxembourg to Lisbon

Do I need an onward ticket to enter Luxembourg?

The application must be accompanied by the following documents:

-2 recent and identical identity photos; -a valid passport or a travel document accepted in the Schengen area, which is valid for at least 3 months after the expiry date of the requested visa; -supporting documents associated with the purpose of the journey, such as: -legalised affidavit of support from the host in Luxembourg; -a return airline ticket;