Perhaps you should try some spelling variations:
cua triet » cua viet, su triet, va triet
van hanh » van thanh, ban hanh, van anh
hanh vai » hanh vi, hanh va, hanh tai
su sach » so sach, vu sach
ky sang » ky dang, ky tang, duy sang
mai hoi » mai khoi, dai hoi, lai hoi
hieu va » lieu va, hieu qua
cac thu » cach thuc, cac thoi
thu van » thuc van, thuy van, tu van
cua tre » cua te, cuu tre, dua tren

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 ((ky sang) or (ky nang)) mai hoi. hieu va cac thu van hanh vai ((cua tre) OR (cua triet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((ky sang) OR (ky nang)) mai hoi. hieu va cac thu van hanh vai ((cua tre) OR (cua triet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((ky sang) or (ky nang)) mai hoi. hieu va cac thu van hanh vai ((cua tre) OR (cua triet))".
• Adding a wildcard symbol may retrieve word variants: su sach ((ky sang) or (ky nang)) mai hoi. hieu va cac thu van hanh vai ((cua tre) OR (cua triet))*.