Perhaps you should try some spelling variations:
thu sach » thuat sach, thuoc sach, thu hoach
hieu van » hieu va, thien van, hieu ve
cham tuc » nham thuc, pham thuc, tham thuc
hanh vai » hanh vi, hanh va, hanh tai
tu sach » su sach, te sach, tu cach
cao hoi » cau hoi, co hoi, cao hoc
va hanh » van hanh, va thanh, va danh
tuc va » thuc va, truc va, tuc xa
vai va » mai va, dai va, hai va
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 (thu sach)) ky nang cao hoi. ((hieu van) or (lieu va)) cham tuc va hanh vai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) ky nang cao hoi. ((hieu van) OR (lieu va)) cham tuc va hanh vai va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (thu sach)) ky nang cao hoi. ((hieu van) or (lieu va)) cham tuc va hanh vai va thiet".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) OR (thu sach)) ky nang cao hoi. ((hieu van) or (lieu va)) cham tuc va hanh vai va thiet*.