Perhaps you should try some spelling variations:
interaction theorems » integration theorems, interaction terms, interaction theory
immigration policies » immigration policy, migration policy
growth immigration » growth migration, gross immigration, from immigration
how interaction » flow interaction, how interactive, from interaction

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (( supply how interaction theorems. ) or ( supply growth immigration policies. ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( supply how interaction theorems. ) OR ( supply growth immigration policies. )).
• Adding a wildcard symbol may retrieve word variants: (( supply how interaction theorems. ) or ( supply growth immigration policies. ))*.