Perhaps you should try some spelling variations:
cac quoc » cac nuoc, cac cuoc, cao quoc
hanh hai » thanh hai, nhanh hai, hang hai
lan hanh » ban hanh, van hanh, lan anh
quoc lan » quoc ban, nuoc luan, quoc quan
hieu van » hieu va, thien van, lieu va
cua tre » cua te, cua triet, dua tren
van cac » van hac, van cau, van bac
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 cac quoc lan 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 cac quoc lan 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 cac quoc lan hanh hai ((cua tre) or (cuu tre))*.