Perhaps you should try some spelling variations:
"adf working papers; working paper" » "off working papers; working paper", "staff working papers; working paper"
"imf working papers; working paper" » "off working papers; working paper", "brief working papers; working paper"
"hf working papers; working paper" » "off working papers; working paper"

Try widening your search to All Fields.

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: (("hf working papers; working paper") OR ((("adf working papers; working paper") OR ("imf working papers; working paper")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"hf working papers; working paper\") or (((\"adf working papers; working paper\") OR (\"imf working papers; working paper\"))))".
• Removing quotes may allow a broader search: (( hf working papers; working paper ) or ((( adf working papers; working paper ) OR ( imf working papers; working paper )))).
• Adding a wildcard symbol may retrieve word variants: (("hf working papers; working paper") or ((("adf working papers; working paper") OR ("imf working papers; working paper"))))*.