Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
kho tang » cao tang
tu sach » thu sach, su sach, te sach
cua tre » cua te, cua triet, dua tren
duc van » duc va, duc tan, duc manh
cam duc » cam xuc, cao duc, pham duc
cuu tre » cau tren, cau treo
hieu va » lieu va, hieu qua
ky tang » ky nang, ky dang, ky trong
va cam » va cham, va cac, va cao

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 tang) OR (kho tang)) xa hoi. hieu va cam duc van hanh vi ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky tang) OR (kho tang)) xa hoi. hieu va cam duc van hanh vi ((cua tre) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ky tang) OR (kho tang)) xa hoi. hieu va cam duc van hanh vi ((cua tre) or (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ky tang) OR (kho tang)) xa hoi. hieu va cam duc van hanh vi ((cua tre) or (cuu tre))*.