Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien cac » vien bach, vien dai, vien da
van dinh » van minh, van dich, xuan dinh
vai cua » dai cua, hai cua, lai cua
va dinh » va kinh, va tinh, vu dinh
cua tre » cua te, cuu tre, cua triet
nang ma » tang ma, nang cao, mang may
sang ma » tang ma, sang tao, mang may
sac ky » cac ky, sai ky
cac lo » cac lop, cac co, cac bo
te sac » te sach, te cac, te san

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sac ky ((nang ma) or (sang ma)) hoi. hieu vien cac lo ((va dinh) OR (van dinh)) vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sac ky ((nang ma) OR (sang ma)) hoi. hieu vien cac lo ((va dinh) OR (van dinh)) vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sac ky ((nang ma) or (sang ma)) hoi. hieu vien cac lo ((va dinh) OR (van dinh)) vai cua tre".
• Adding a wildcard symbol may retrieve word variants: te sac ky ((nang ma) or (sang ma)) hoi. hieu vien cac lo ((va dinh) OR (van dinh)) vai cua tre*.