Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
vu sach » vu bach, su sach, vu khach
cao hoi » cau hoi, co hoi, cao hoc
hieu va » lieu va, hieu qua
cac duc » cac du, cao duc, cac dac
va hanh » van hanh, va thanh, va danh
hanh vu » hanh vi, hanh va, hanh tu
vu va » vu van, tu va, su va

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

• Performing a fuzzy search may retrieve terms with similar spellings: "((thu sach) or (vu sach)) ky nang cao hoi. hieu va cac duc va hanh vu va (thiet" OR thieu")~.
• If you are trying to use Boolean operators, they must be ALL CAPS: "((thu sach) OR (vu sach)) ky nang cao hoi. hieu va cac duc va hanh vu va (thiet" OR thieu").
• Removing quotes may allow a broader search: ((thu sach) or (vu sach)) ky nang cao hoi. hieu va cac duc va hanh vu va (thiet OR thieu ).
• Adding a wildcard symbol may retrieve word variants: "((thu sach) or (vu sach)) ky nang cao hoi. hieu va cac duc va hanh vu va (thiet" OR thieu")*.