Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
thu sach » thuat sach, thuoc sach, thu hoach
hanh vai » hanh vi, hanh va, hanh tai
sang dai » sang tai, lang dai, sang mai
tu sach » su sach, te sach, tu cach
vai cua » dai cua, hai cua, lai cua
va hanh » van hanh, va thanh, va danh
dai hai » dai han, dai hoi, dai tai
ky sang » ky nang, ky dang, ky tang
cua tre » cua te, cuu tre, cua triet
da tuc » dao tuc, da tac, da tu
va tuc » va thuc, va tu, va tac

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 sang dai hai. hieu vien ((da tuc) or (va tuc)) va hanh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) ky sang dai hai. hieu vien ((da tuc) OR (va tuc)) va hanh vai cua tre.
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu sach)) ky sang dai hai. hieu vien ((da tuc) or (va tuc)) va hanh vai cua tre*.