Perhaps you should try some spelling variations:
contract based » control based, content based, context based
study contract » study contracting, study context, study abstract
yang study » yang judy, arg study
saw young » a young, how young, jae young
yao yang » yang yang
ad young » a young, jae young, all young

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

• Performing a fuzzy search may retrieve terms with similar spellings: (wan or wing) yao yang study contract based ((ad young) OR (saw young)) ghi ;~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (wan OR wing) yao yang study contract based ((ad young) OR (saw young)) ghi ;.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(wan or wing) yao yang study contract based ((ad young) OR (saw young)) ghi ;".
• Adding a wildcard symbol may retrieve word variants: (wan or wing) yao yang study contract based ((ad young) OR (saw young)) ghi ;*.