Perhaps you should try some spelling variations:
sach thue » sach thu, sach thieu, sach tham
thue nang » thien nang, thuat nang, thi nang
doc sach » hoc sach, toc sach, nuoc sach
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
thuc ban » thuoc ban, thuc dan, thu ban
ban ban » ban banh, van ban, can ban
cua tre » cuu tre, cua triet, dua tren
ban vi » ban voi, ban va, ban ve
cua tu » cua tuc, cua su, cua cu
x hoi » xa hoi, o hoi, x ho

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc sach thue nang x hoi. hieu van nam thuc ban ban vi ((cua tre) or (((cua te) or (cua tu))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach thue nang x hoi. hieu van nam thuc ban ban vi ((cua tre) OR (((cua te) OR (cua tu)))).
• Adding a wildcard symbol may retrieve word variants: doc sach thue nang x hoi. hieu van nam thuc ban ban vi ((cua tre) or (((cua te) or (cua tu))))*.