Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
dau tren » dau tien, dat tren, dau tieng
su sach » so sach, vu sach
sach ty » sach y, sach tu, sach thu
nang xa » nang x, lang xa, mang xa
nang ma » tang ma, sang ma, nang cao
dau tuc » dau tu, dao tuc, cau truc
tuc van » thuc van, truc van, tuc va
hanh di » hanh vi, hanh de, hang di
va dau » va dao
di dau » doi dau, bi dau, di du

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ty ((nang xa) or (nang ma)) hoi. lieu va dau tuc van hanh di dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty ((nang xa) OR (nang ma)) hoi. lieu va dau tuc van hanh di dau tren*.