Perhaps you should try some spelling variations:
economics development » economic development, economic developments
boarding passes » boarding pass, boarding houses, boarding process
oecd economics » oecd economic, oecd economies, kcd economics
working papers » working paper

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: oecd economics development ((working papers) OR (boarding passes)).
• Adding a wildcard symbol may retrieve word variants: oecd economics development ((working papers) or (boarding passes))*.