Perhaps you should try some spelling variations:
studien der » studien des, studie der, studien uber
i studien » ii studien, 3 studien, ii studies
amin hong » min hong, among hong, asia hong
tin hong » tan hong, kia hong, thi hong
yang yi » yang xi, yang jui
der a » der _, der e
a i » am i, a im
tan » than

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: ((((yang yi) OR (yang dean))) OR (yang di))a i studien der a ((amin hong) OR (tin hong)) tan ;~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((yang yi) or (yang dean))) or (yang di))a i studien der a ((amin hong) OR (tin hong)) tan ;~".
• Adding a wildcard symbol may retrieve word variants: ((((yang yi) or (yang dean))) or (yang di))a i studien der a ((amin hong) OR (tin hong)) tan ;*.