Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
tu sach » thu sach, su sach, te sach
hieu ve » hieu va, hieu van
co hoi » co hoc, co loi
v nang » va nang, vu nang, van nang
y nang » ky nang, ly nang, may nang
ve cac » va cac, vien cac
tuc va » thuc va, truc va, duc va
vi dau » vi dai, va dau, bi dau

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

• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((y nang) OR (v nang)) co hoi. hieu ve cac ((tuc va) OR (tuc xa)) hanh vi dau tren~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((y nang) or (v nang)) co hoi. hieu ve cac ((tuc va) OR (tuc xa)) hanh vi dau tren~".
• Adding a wildcard symbol may retrieve word variants: tu sach ((y nang) or (v nang)) co hoi. hieu ve cac ((tuc va) OR (tuc xa)) hanh vi dau tren*.