Perhaps you should try some spelling variations:
yan yang » yang yang, yao yang, dan yang
yang oil » yang zili, yang di, yang xi
oil coal » oil cost, oil oil, oil can
coal plf » coal fly, coal pit
hong hai » shang hai, zhong tai, dang hai
plf oil » palm oil, gulf oil, plam oil
hong yu » wong yue
wang » wing, wan, lang

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

• Performing a fuzzy search may retrieve terms with similar spellings: wang yan yang oil coal plf oil ((hong hai) or (hong yu)) ;~.
• If you are trying to use Boolean operators, they must be ALL CAPS: wang yan yang oil coal plf oil ((hong hai) OR (hong yu)) ;.
• Adding a wildcard symbol may retrieve word variants: wang yan yang oil coal plf oil ((hong hai) or (hong yu)) ;*.