Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
nang tai » hang tai, tang tai, sang tai
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
va hanh » va thanh, va danh, ban hanh
vai cua » dai cua, hai cua, lai cua
vien da » vien dai, hien dai
cua tre » cua te, cuu tre, cua triet
tai hai » thi hai, dai hai, tai ha
da tuc » dao tuc, va tuc, da 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 hoach)) ky nang tai hai. hieu vien da tuc ((va hanh) OR (van hanh)) vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu hoach)) ky nang tai hai. hieu vien da tuc ((va hanh) OR (van hanh)) vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (thu hoach)) ky nang tai hai. hieu vien da tuc ((va hanh) OR (van hanh)) vai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu hoach)) ky nang tai hai. hieu vien da tuc ((va hanh) OR (van hanh)) vai cua tre*.