Perhaps you should try some spelling variations:
cam quoc » cac quoc, cao quoc, nam quoc
hang hai » hoang hai, hang tai, thanh hai
hanh hai » thanh hai, nhanh hai, hanh tai
quoc ban » quoc bao, quoc lan, quoc quan
hieu van » hieu va, thien van, lieu va
van cam » van nam, van lam, van cau
sach ky » sach y, sach ty, sach kem
lang xa » lang ha, dang xay, lang van
cua tre » cua te, cuu tre, cua triet
sac ky » cac ky, sai ky

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 (sac ky)) lang xa hoi. hieu van cam quoc ban ((hanh hai) OR (hang hai)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sac ky)) lang xa hoi. hieu van cam quoc ban ((hanh hai) OR (hang hai)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) or (sac ky)) lang xa hoi. hieu van cam quoc ban ((hanh hai) OR (hang hai)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) or (sac ky)) lang xa hoi. hieu van cam quoc ban ((hanh hai) OR (hang hai)) cua tre*.