Perhaps you should try some spelling variations:
dua tren » dung tren
van hanh » van thanh, ban hanh, van anh
cuu tre » cua tre, cau tren, cau treo
cham oc » cham soc, cham o, cham hoi
sach ty » sach y, sach tu, sach thu
hieu va » lieu va, hieu qua
te sach » toc sach
nang xa » lang xa, nang ma, mang xa
va cham » va chat, va tham
oc van » hoc van, luoc van, quoc van

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ty ((nang xa) or (nang x)) hoi. hieu va cham oc van hanh vi ((cuu tre) or (dua tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ty ((nang xa) OR (nang x)) hoi. hieu va cham oc van hanh vi ((cuu tre) OR (dua tren)).
• Adding a wildcard symbol may retrieve word variants: te sach ty ((nang xa) or (nang x)) hoi. hieu va cham oc van hanh vi ((cuu tre) or (dua tren))*.