Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
tay lang » tai lang, tay tang, tay quang
hanh de » hanh ve, hanh kem
dau tuc » dau tu, dao tuc, cau truc
su sach » so sach, vu sach
ty lang » ty xang, ty hang, tu lang
tuc va » thuc va, truc va, tuc xa
va dau » va dao

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ((ty lang) OR (tay lang)) xa hoi. lieu va dau tuc va ((hanh vi) or (hanh de)) cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((ty lang) OR (tay lang)) xa hoi. lieu va dau tuc va ((hanh vi) OR (hanh de)) cau tren*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((ty lang) OR (tay lang)) xa hoi. lieu va dau tuc va ((hanh vi) or (hanh de)) cau tren*".