Perhaps you should try some spelling variations:
dat tren » dat trong, dua tren
cau treo » cau theo, cau tren, cau triet
van hanh » van thanh, ban hanh, van anh
nhan luc » nang luc
hieu ve » hieu va, hieu van
ve nhan » ve nha, de nhan, va nhan
luc van » luoc van, luu van, duc van
hanh ke » hanh kem, thanh ke, hanh ky
nang xa » lang xa, nang ma, mang xa
sac ky » cac ky, sai ky
tu sac » tu sach, tu cac, tu san

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sac ky ((nang xa) or (nang x)) hoi. hieu ve nhan luc van hanh ke ((cau treo) or (dat tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky ((nang xa) OR (nang x)) hoi. hieu ve nhan luc van hanh ke ((cau treo) OR (dat tren)).
• Adding a wildcard symbol may retrieve word variants: tu sac ky ((nang xa) or (nang x)) hoi. hieu ve nhan luc van hanh ke ((cau treo) or (dat tren))*.