Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
thu sach » thuat sach, thuoc sach, thu hoach
tu sach » su sach, te sach, tu cach
duc van » duc va, duc tan, duc manh
cam duc » cam xuc, cao duc, pham duc
hieu va » lieu va
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
cua tre » cua te, cuu tre, cua triet
vi cua » vai cua, di cua

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