Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
xanh di » vanh dai, xanh tai
danh di » danh du, danh dien, danh gia
hieu ve » hieu va, hieu van
te sach » toc sach
cac tuc » cac toc, cac tu, cac tac
nang ma » tang ma, sang ma, nang cao
ve cac » va cac, vien cac
tuc va » thuc va, truc va, tuc xa

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: te sach y ((nang x) OR (nang ma)) hoi. hieu ve cac tuc va ((danh di) OR (xanh di)) cau tren~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach y ((nang x) or (nang ma)) hoi. hieu ve cac tuc va ((danh di) OR (xanh di)) cau tren~".
• Adding a wildcard symbol may retrieve word variants: te sach y ((nang x) or (nang ma)) hoi. hieu ve cac tuc va ((danh di) OR (xanh di)) cau tren*.