Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
tai khoi » tai khoa, mai khoi, tao khoi
kien cua » khien cua, dien cua, tien cua
dan kien » danh kien, van kien, dan vien
vu pham » su pham, vi pham, vu kham
hieu vu » hieu va, hieu ve, hieu su
cua tre » cua te, cuu tre, cua triet
tai hoi » dai hoi, tai hai, tai hoe
va nang » van nang, da nang, cam nang
va dan » ca dan, va dao, va dau
v nang » vu nang, van nang, voi nang

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ((v nang) or (va nang)) ((tai hoi) or (tai khoi)). hieu vu pham duc va dan kien cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((v nang) OR (va nang)) ((tai hoi) OR (tai khoi)). hieu vu pham duc va dan kien cua tre.
• Adding a wildcard symbol may retrieve word variants: toc sach ((v nang) or (va nang)) ((tai hoi) or (tai khoi)). hieu vu pham duc va dan kien cua tre*.