Perhaps you should try some spelling variations:
thien van » thi van
toc sach » hoc sach, doc sach, thuoc sach
hanh lai » hanh lam, hanh tai, thanh lap
tham duc » pham duc, tham du, than duc
hieu va » lieu va, hieu qua
lai cua » dai cua, hai cua, lai chau
va hanh » van hanh, va thanh, va danh
cao hoi » cau hoi, co hoi, cao hoc
ty nang » ky nang, ty xang, ty hang
cua tre » cua te, cuu tre, cua triet

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

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