Perhaps you should try some spelling variations:
critical nucleus » critical nuclear, critical nucleases, critical numbers
tactical nuclear » statistical nuclear, clinical nuclear, national nuclear
practice nuclear » practical nuclear, practice nucleic, particle nuclear
ban treaty » a treaty
test ban » west bank, test bed

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: ((((critical nucleus) OR (tactical nuclear))) OR (practice nuclear)) test ban treaty.
• Adding a wildcard symbol may retrieve word variants: ((((critical nucleus) or (tactical nuclear))) or (practice nuclear)) test ban treaty*.