Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
dua tren » dung tren
cau tren » cu tren, dau tren, ca tren
so sach » so sanh, bo sach, co sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
ba truc » cau truc, ba trung, dai truc
truc va » thuc va, thuc vat, trung va
van ba » van ban, van bao, van bac
va dan » ca dan, va dao, va dau
dan vi » doan vi, don vi, dan va

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ky nang xa hoi. hieu van ba truc va dan vi ((dua tren) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky nang xa hoi. hieu van ba truc va dan vi ((dua tren) OR (cau tren)).
• Adding a wildcard symbol may retrieve word variants: so sach ky nang xa hoi. hieu van ba truc va dan vi ((dua tren) or (cau tren))*.