Perhaps you should try some spelling variations:
hoang hai » hoang thi, hoang van
thuc van » thuc dan, thuc va, thuc hanh
tu cach » tu cac
so sach » so sanh, bo sach, co sach
hieu vu » hieu va, hieu ve, hieu su
vu pham » su pham, vi pham, vu kham
hai cua » thai cua, dai cua, hoi cua
cua te » cua tu
x hoi » xa hoi, o hoi, x ho

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu cach) or (so sach)) ky nang x hoi. hieu vu pham ((thuc van) OR (thuc vat)) hoang hai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu cach) OR (so sach)) ky nang x hoi. hieu vu pham ((thuc van) OR (thuc vat)) hoang hai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu cach) or (so sach)) ky nang x hoi. hieu vu pham ((thuc van) OR (thuc vat)) hoang hai cua te".
• Adding a wildcard symbol may retrieve word variants: ((tu cach) or (so sach)) ky nang x hoi. hieu vu pham ((thuc van) OR (thuc vat)) hoang hai cua te*.