Perhaps you should try some spelling variations:
"aei studies on series treaty negotiations." » "aei studies on series trade negotiation.", "aei studies on series peace negotiations.", "aei studies on series debt negotiations.", "aei studies on series trends negotiations."
"aei studies on service trade negotiations." » "aei studies on services trade negotiations."

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: (("aei studies on series treaty negotiations.") OR ("aei studies on service trade negotiations."))~.
• Removing quotes may allow a broader search: (( aei studies on series treaty negotiations. ) or ( aei studies on service trade negotiations. ))~.
• Adding a wildcard symbol may retrieve word variants: (("aei studies on series treaty negotiations.") or ("aei studies on service trade negotiations."))*.