Perhaps you should try some spelling variations:
harvard world » harvard cold
studies force » studies formal, studies from, studies food
force surveys » force survey, firm surveys
world urban » worst urban
studies pre » studies part, studies pt, studies die
pre surveys » pre survey, re surveys, tie surveys

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( harvard world urban studies force surveys. ) or ( harvard world urban studies pre surveys. ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( harvard world urban studies force surveys. ) OR ( harvard world urban studies pre surveys. )).
• Adding a wildcard symbol may retrieve word variants: (( harvard world urban studies force surveys. ) or ( harvard world urban studies pre surveys. ))*.