Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
hanh lai » hanh lam, hanh tai, thanh lap
su triet » su viet, su tien, ve triet
su sach » so sach, vu sach
sach tu » sach thu, cach tu, sach ty
tu nang » tru nang, tu nong, tu nano
hieu va » lieu va, hieu qua
va cham » va chat, va tham
cham xu » chao xu, cham cuu, chat xuc
xu van » tu van, vu van, su van
o hoi » co hoi, o hoc, o hoa
o hai » co hai, so hai, o lai

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 tu nang ((o hoi) or (o hai)). hieu va cham xu van hanh lai su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach tu nang ((o hoi) OR (o hai)). hieu va cham xu van hanh lai su triet.
• Adding a wildcard symbol may retrieve word variants: su sach tu nang ((o hoi) or (o hai)). hieu va cham xu van hanh lai su triet*.