Perhaps you should try some spelling variations:
literature author » literature arts
literature oral » literature moral, literatura oral, literature morals
key literature » grey literature, gray literature, body literature
159 agenda » 1979 agenda, 10 agenda, 12 agenda
1 agenda » _ agenda, 7 agenda, 3 agenda
2 benda » 2 bends

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: (( ((159 agenda) OR (1 agenda)) i a literature oral ) OR ( 2 benda _ key literature author )).
• Adding a wildcard symbol may retrieve word variants: (( ((159 agenda) or (1 agenda)) i a literature oral ) or ( 2 benda _ key literature author ))*.