Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
thu sach » thuat sach, thuoc sach, thu hoach
xanh di » danh di, vanh dai, xanh tai
va xanh » va danh, va hanh, va anh
cac duc » cac du, cao duc, cac dac
hieu va » lieu va, hieu qua
tu sach » su sach, te sach, tu cach
di cau » da cau, diem cau
o hai » co hai, so hai, o lai
o hoi » co hoi, o hoc, o hoa

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) OR (thu sach)) ky nang ((o hoi) OR (o hai)). hieu va cac duc va xanh di cau tren~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (thu sach)) ky nang ((o hoi) OR (o hai)). hieu va cac duc va xanh di cau tren~".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu sach)) ky nang ((o hoi) OR (o hai)). hieu va cac duc va xanh di cau tren*.