Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, hieu ve
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
van dinh » van minh, van dich, xuan dinh
so sach » so sanh, bo sach, co sach
sach ty » sach y, sach tu, sach thu
xang xa » lang xa, mang xa, ang xa
va dinh » va kinh, va tinh, vu dinh
vai cua » dai cua, hai cua, lai cua
cua te » cua tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ty xang xa hoi. ((hieu van) or (lieu va)) cac nuoc ((van dinh) OR (va dinh)) vai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ty xang xa hoi. ((hieu van) OR (lieu va)) cac nuoc ((van dinh) OR (va dinh)) vai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ty xang xa hoi. ((hieu van) or (lieu va)) cac nuoc ((van dinh) OR (va dinh)) vai cua te".
• Adding a wildcard symbol may retrieve word variants: so sach ty xang xa hoi. ((hieu van) or (lieu va)) cac nuoc ((van dinh) OR (va dinh)) vai cua te*.