Perhaps you should try some spelling variations:
hieu hien » bieu hien, dieu hien, chieu chien
hieu vien » hieu viec, thieu nien, hieu tieng
thu sach » thuat sach, thuoc sach, thu hoach
hanh vai » hanh vi, hanh va, hanh tai
sang tai » hang tai, sang tao, tang tai
tu sach » su sach, te sach, tu cach
vai cua » dai cua, hai cua, lai cua
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
tai hai » thi hai, dai hai, tai ha
ky sang » ky nang, ky dang, ky tang
da tuc » dao tuc, va tuc, da tac
tuc va » thuc va, truc va, tuc xa

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 tai hai. ((hieu vien) OR (hieu hien)) da 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 tai hai. ((hieu vien) OR (hieu hien)) da tuc va hanh vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (thu sach)) ky sang tai hai. ((hieu vien) OR (hieu hien)) da tuc va hanh vai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu sach)) ky sang tai hai. ((hieu vien) OR (hieu hien)) da tuc va hanh vai cua tre*.