Perhaps you should try some spelling variations:
"world manko working paper" » "world django working paper", "world manner working paper", "world manual working paper", "world many working paper", "world make working paper", "world mark working paper"
"world manko working papers" » "world django working papers", "world manner working papers", "world manual working papers", "world many working papers", "world make working papers", "world mark working papers"
"world macro working paper" » "world macros working paper", "world mac working paper", "world avro working paper", "word macro working paper", "world mark 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: (((("world manko working paper") OR ("world manko working papers"))) OR ("world macro working paper")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"world manko working paper\") OR (\"world manko working papers\"))) or (\"world macro working paper\"))".
• Removing quotes may allow a broader search: (((( world manko working paper ) OR ( world manko working papers ))) or ( world macro working paper )).
• Adding a wildcard symbol may retrieve word variants: (((("world manko working paper") OR ("world manko working papers"))) or ("world macro working paper"))*.