Perhaps you should try some spelling variations:
cua triet » cua viet, su triet, va triet
thu sach » tu sach, thuat sach, thuoc sach
van cac » van hac, van bac, dan cac
van cau » van dau, van hau, van chat
va hanh » van hanh, va thanh, va danh
hanh di » hanh vi, hanh de, hang di
cua tre » cua te, cuu tre, dua tren
y nang » ky nang, ly nang, v nang
x hoi » xa hoi, o hoi, x ho
du va » dau va, tu va, su va

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach y nang x hoi. hieu ((van cac) or (van cau)) du va hanh di ((cua tre) OR (cua triet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach y nang x hoi. hieu ((van cac) OR (van cau)) du va hanh di ((cua tre) OR (cua triet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach y nang x hoi. hieu ((van cac) or (van cau)) du va hanh di ((cua tre) OR (cua triet))".
• Adding a wildcard symbol may retrieve word variants: thu sach y nang x hoi. hieu ((van cac) or (van cau)) du va hanh di ((cua tre) OR (cua triet))*.