Perhaps you should try some spelling variations:
nhan than » nhan thanh, khan than, nhan chan
hieu van » hieu va, thien van, lieu va
cam thuc » nam thuc, cam thu, can thuc
hat nhan » ca nhan, tao nhan, van nhan
than cua » nhan cua, thai cua, ban cua
cao hoi » cau hoi, co hoi, cao hoc
cua tre » cua te, cuu tre, cua triet
sach v » sach va, sach 2, sach vay

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 v) or (sach y)) nang cao hoi. hieu van ((cam thuc) or (am thuc)) hat nhan than cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach v) OR (sach y)) nang cao hoi. hieu van ((cam thuc) OR (am thuc)) hat nhan than cua tre.
• Adding a wildcard symbol may retrieve word variants: su ((sach v) or (sach y)) nang cao hoi. hieu van ((cam thuc) or (am thuc)) hat nhan than cua tre*.