Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
cau treo » cau theo, cau tren, cau triet
van hanh » van thanh, ban hanh, van anh
hieu van » hieu va, thien van, lieu va
lang xa » lang ha, dang xay, lang van
sach ty » sach y, sach tu, sach thu
nam luc » nang luc, nhan luc, nam thuc
luc van » luoc van, luu van, duc van
nang xa » nang x, nang ma, mang xa
hanh di » hanh vi, hanh de, hang di
tu sach » thu sach, su sach, te sach

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 ty ((nang xa) or (lang xa)) hoi. hieu van nam luc van hanh di ((cau treo) or (dau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty ((nang xa) OR (lang xa)) hoi. hieu van nam luc van hanh di ((cau treo) OR (dau tren)).
• Adding a wildcard symbol may retrieve word variants: tu sach ty ((nang xa) or (lang xa)) hoi. hieu van nam luc van hanh di ((cau treo) or (dau tren))*.