Perhaps you should try some spelling variations:
thuat sach » thuat lanh, thuat san
thu sach » tu sach, thuoc sach, thu hoach
van hanh » van thanh, ban hanh, van anh
hieu van » thien van, lieu va, hieu ve
hieu va » lieu va, hieu qua
hanh di » hanh vi, hanh de, hang di
duc van » duc va, duc tan, duc manh
hac duc » hoc duc, ha duc, thach duc
cua tre » cua te, cuu tre, cua triet
ty nang » ky nang, ty xang, ty hang
di cua » dai cua, doi cua, de cua
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: ((thu sach) or (thuat sach)) ty nang x hoi. ((hieu van) OR (hieu va)) hac duc van hanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((thu sach) OR (thuat sach)) ty nang x hoi. ((hieu van) OR (hieu va)) hac duc van hanh di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((thu sach) or (thuat sach)) ty nang x hoi. ((hieu van) OR (hieu va)) hac duc van hanh di cua tre".
• Adding a wildcard symbol may retrieve word variants: ((thu sach) or (thuat sach)) ty nang x hoi. ((hieu van) OR (hieu va)) hac duc van hanh di cua tre*.