Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
nhan tai » hang tai, van tai, toan tai
day nhan » day nhanh, dac nhan, dam nhan
thuc day » thuc dan, thuc vat
nam thuc » nam thuoc, am thuc, nam thu
cua tre » cua te, cuu tre, cua triet
so sach » so sanh, bo sach, co sach
sach ly » sach y, sach lo, sach ty
hang ca » hang va, nang cao, hang tai
hang xa » hoang xa, hang va, lang xa
cu tren » tu tren, dua tren

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 ly ((hang xa) or (hang ca)) hoi. hieu van nam thuc day nhan tai ((cua tre) or (cu tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ly ((hang xa) OR (hang ca)) hoi. hieu van nam thuc day nhan tai ((cua tre) OR (cu tren)).
• Adding a wildcard symbol may retrieve word variants: so sach ly ((hang xa) or (hang ca)) hoi. hieu van nam thuc day nhan tai ((cua tre) or (cu tren))*.