Perhaps you should try some spelling variations:
german gender » german lander, germany under, german border
human gender » bhutan gender, human gene, human genome
wang dan » wang yan, wang ban, wang yidan
dan yang » daun yang, tan yang, wang yang
cong sun » cong shu, cong van, wing sun
von see » von seo, von seu, von sex

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 dan yang ((human gender) OR (german gender)) bank minh ((von see) OR (cong sun)) ;~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "wang dan yang ((human gender) OR (german gender)) bank minh ((von see) or (cong sun)) ;~".
• Adding a wildcard symbol may retrieve word variants: wang dan yang ((human gender) OR (german gender)) bank minh ((von see) or (cong sun)) ;*.