Perhaps you should try some spelling variations:
early studies » earlier studies, early stages
studies force » studies formal, studies from, studies food
force surveys » force survey, firm surveys
studies fuel » studies cruel, studies field, studies from
fuel sources » fuel source
cold early » world early, bord early, good early

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

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