Perhaps you should try some spelling variations:
su triet » su viet, su tien
ve triet » va trien
tu sach » thu sach, su sach, te sach
sach tu » sach thu, cach tu, sach ty
tu cong » thu cong, te cong, tai cong
hieu va » lieu va, hieu qua
va pham » van pham, va phat, va phap
va hanh » van hanh, va thanh, va danh
hanh te » hanh tu, hanh ve, hanh de
cong o » cong so, cong co, cong bo
o hoi » co hoi, o hoc, o hai

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach tu cong o hoi. hieu va pham duc va hanh te ((su triet) or (ve triet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach tu cong o hoi. hieu va pham duc va hanh te ((su triet) OR (ve triet)).
• Adding a wildcard symbol may retrieve word variants: tu sach tu cong o hoi. hieu va pham duc va hanh te ((su triet) or (ve triet))*.