Perhaps you should try some spelling variations:
vien cac » vien bach, vien dai, vien da
sach ky » sac ky, sach ty, sach kem
cuu tre » cua tre, cau tren, cau treo
ve cac » va cac
va dao » ca dao
dao vi » dao voi, dao ve, dao va
vi cuu » vi luu, vinh cuu
x hoi » xa hoi, o hoi, x ho
su va » su van, tu va

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) or (sach y)) nang x hoi. hieu ((ve cac) OR (vien cac)) su va dao vi cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sach y)) nang x hoi. hieu ((ve cac) OR (vien cac)) su va dao vi cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) or (sach y)) nang x hoi. hieu ((ve cac) OR (vien cac)) su va dao vi cuu tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) or (sach y)) nang x hoi. hieu ((ve cac) OR (vien cac)) su va dao vi cuu tre*.