Perhaps you should try some spelling variations:
treaty change » create change, real change, area change
trend change » trends changhe, around change, trend chapter
wang liang » wang yang
liang yan » liang dan, liang tan, liang ying
wong yue » wang yue, hong yu
yan oil » can oil, oman oil, than oil

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

• If you are trying to use Boolean operators, they must be ALL CAPS: wang liang yan oil ((trend change) OR (treaty change)) li ((hong tan) OR (wong yue)) ;~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "wang liang yan oil ((trend change) OR (treaty change)) li ((hong tan) or (wong yue)) ;~".
• Adding a wildcard symbol may retrieve word variants: wang liang yan oil ((trend change) OR (treaty change)) li ((hong tan) or (wong yue)) ;*.