Perhaps you should try some spelling variations:
quoc quan » qua quan, luc quan, hoc quan
quoc ban » quoc bao, quoc lan, quoc binh
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
cua tre » cua te, cuu tre, cua triet
va cam » va cham, va cac, va cao
anh de » hanh de, anh d, anh ve
de cua » le cua, te cua, dieu cua
x hoi » xa hoi, x ho, 5 hoi
o hoi » co hoi, o hoc, o hai

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 ((x hoi) or (o hoi)). lieu va cam ((quoc ban) OR (quoc quan)) anh de cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang ((x hoi) OR (o hoi)). lieu va cam ((quoc ban) OR (quoc quan)) anh de cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang ((x hoi) or (o hoi)). lieu va cam ((quoc ban) OR (quoc quan)) anh de cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang ((x hoi) or (o hoi)). lieu va cam ((quoc ban) OR (quoc quan)) anh de cua tre*.