Perhaps you should try some spelling variations:
"general migration status studies." » "internal migration status studies.", "external migration status studies.", "general education status studies.", "general migration rates studies.", "general migration studies studies.", "general nutrition status studies.", "general migration state studies.", "general migration status series.", "general migration soas studies."
"illegal immigration status studies." » "illegal immigration rates studies.", "illegal immigration studies studies.", "illegal imnutrition status studies.", "illegal immigration state studies.", "illegal immigration status series.", "illegal immigration soas studies."

Try widening your search to All Fields.

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("illegal immigration status studies.") or ("general migration status studies."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("illegal immigration status studies.") OR ("general migration status studies.")).
• Removing quotes may allow a broader search: (( illegal immigration status studies. ) or ( general migration status studies. )).
• Adding a wildcard symbol may retrieve word variants: (("illegal immigration status studies.") or ("general migration status studies."))*.