Perhaps you should try some spelling variations:
chat thien » phat trien, cai thien, phat hien
chat triet » chet triet, phat trien, cua triet
hieu van » hieu va, thien van, lieu va
chu duc » thu duc, chua duoc, cuu duoc
hanh va » hang va, hanh vi
va hanh » van hanh, va thanh, va danh
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
van chu » van chi, van phu, van cau
o hai » co hai, so hai, o lai
o hoi » co hoi, o hoc, o hoa

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