Perhaps you should try some spelling variations:
nam quoc » nam duoc, nam buoc, nam thuoc
hieu van » hieu va, thien van, lieu va
hanh hai » thanh hai, nhanh hai, hang hai
ban hanh » ban hang
quoc ban » quoc bao, quoc lan, quoc quan
cua tre » cua te, cua triet, dua tren
sach ky » sach y, sach ty, sach kem
lang xa » lang ha, dang xay, lang van
cuu tre » cau tren, cau treo
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 nam quoc ban hanh hai ((cua tre) or (cuu 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 nam quoc ban hanh hai ((cua tre) OR (cuu tre)).
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) or (sac ky)) lang xa hoi. hieu van nam quoc ban hanh hai ((cua tre) or (cuu tre))*.