Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
thanh da » thanh dat, thanh dam, thanh dan
van cham » van chat, van tham, va cham
hieu van » hieu va, thien van, lieu va
lang xa » lang ha, dang xay, lang van
sach ty » sach y, sach tu, sach thu
mang xa » mang may, dang xay, mang cua
soc gia » toc gia, hoc gia, quoc gia
so sach » so sanh, bo sach, co sach
so gia » so giai, so giao, ho gia
da dau » dan dau, dat dau, va dau

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 ((mang xa) or (lang xa)) hoi. hieu van cham ((soc gia) OR (so gia)) thanh da dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ty ((mang xa) OR (lang xa)) hoi. hieu van cham ((soc gia) OR (so gia)) thanh da dau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ty ((mang xa) or (lang xa)) hoi. hieu van cham ((soc gia) OR (so gia)) thanh da dau tren".
• Adding a wildcard symbol may retrieve word variants: so sach ty ((mang xa) or (lang xa)) hoi. hieu van cham ((soc gia) OR (so gia)) thanh da dau tren*.