Perhaps you should try some spelling variations:
hieu cao » chieu cao, hieu cac, hieu ca
thuc van » thuc vat, thuc dan, thuc va
tu sach » thu sach, te sach, tu cach
su sach » so sach, vu sach
cao hoi » cau hoi, co hoi, cao hoc
duc van » duc va, duc tan, duc manh
hanh va » hang va, hanh vi
va va » va van, va vua, va vai
thiet » thieu

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu sach) OR (su sach)) ky nang cao hoi. hieu cao chat ((thuc van) or (duc van)) hanh va va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (su sach)) ky nang cao hoi. hieu cao chat ((thuc van) OR (duc van)) hanh va va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (su sach)) ky nang cao hoi. hieu cao chat ((thuc van) or (duc van)) hanh va va thiet".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) OR (su sach)) ky nang cao hoi. hieu cao chat ((thuc van) or (duc van)) hanh va va thiet*.