Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien cac » vien bach, vien dai, vien da
van hanh » van thanh, ban hanh, van anh
doi cua » dai cua, hoi cua
va hanh » va thanh, va danh, ban hanh
cac hoc » cach hoc, cac hop, bac hoc
cua tre » cua te, cuu tre, cua triet
nang xa » nang x, lang xa, nang ma
lang ha » long ha
sai ky » sac ky
te sai » te tai, te bai, te lai

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sai ky ((nang xa) or (lang ha)) hoi. hieu vien cac hoc ((va hanh) or (van hanh)) doi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sai ky ((nang xa) OR (lang ha)) hoi. hieu vien cac hoc ((va hanh) OR (van hanh)) doi cua tre.
• Adding a wildcard symbol may retrieve word variants: te sai ky ((nang xa) or (lang ha)) hoi. hieu vien cac hoc ((va hanh) or (van hanh)) doi cua tre*.