Perhaps you should try some spelling variations:
thien van » thi van
tu sach » thu sach, su sach, te sach
van cac » van hac, van cau, van bac
van hoi » van hoa, van hoc, van hoe
ky dang » ky nang, ky danh
ky lang » ky nang, ky tang, tay lang
cua tre » cua te, cuu tre, cua triet
xac va » tac va, ac va, bac va
tuc va » thuc va, truc va, tuc xa
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 ((ky lang) OR (ky dang)) van hoi. thien van cac ((xac va) or (tuc va)) hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky lang) OR (ky dang)) van hoi. thien van cac ((xac va) OR (tuc va)) hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ky lang) OR (ky dang)) van hoi. thien van cac ((xac va) or (tuc va)) hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ky lang) OR (ky dang)) van hoi. thien van cac ((xac va) or (tuc va)) hanh vi cua tre*.