Perhaps you should try some spelling variations:
quoc lan » nuoc luan, quoc quan, quoc danh
quoc ban » quoc bao, quoc quan, quoc binh
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
cuu tre » cua tre, cau tren, cau treo
hieu va » lieu va, hieu qua
anh de » hanh de, anh d, anh ve
de cuu » de cua
va cam » va cham, va cac, va cao
o hai » co hai, so hai, o lai

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky nang ((xa hoi) or (o hai)). hieu va cam ((quoc ban) OR (quoc lan)) anh de cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang ((xa hoi) OR (o hai)). hieu va cam ((quoc ban) OR (quoc lan)) anh de cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang ((xa hoi) or (o hai)). hieu va cam ((quoc ban) OR (quoc lan)) anh de cuu tre".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang ((xa hoi) or (o hai)). hieu va cam ((quoc ban) OR (quoc lan)) anh de cuu tre*.