Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
nuoc ban » nuoc san, quoc ban, buoc ban
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
hieu ve » hieu va, hieu van
sach ky » sac ky, sach y, sach ty
ban anh » ban hanh, ban banh, ban danh
cuu tre » cua tre, cau treo
ve cac » va cac, vien cac
anh va » hanh va
x hoi » xa hoi, o hoi, x ho

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