Perhaps you should try some spelling variations:
thu sach » thuat sach, thuoc sach, thu hoach
hieu kem » hieu ky, hieu ve
luc ngan » luc nganh, luc nhan, luat ngan
tu sach » su sach, te sach, tu cach
xang xa » lang xa, mang xa, ang xa
kem cau » ket cau, ke cau, kem chu
cau luc » cau truc, cau phuc
hang vi » hang va, hang di, khang voi
ca tren » cau tren, cu tren, la tren

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) OR (thu sach)) ty xang xa hoi. hieu kem cau luc ngan ((hang vi) or (hanh vi)) ca tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) ty xang xa hoi. hieu kem cau luc ngan ((hang vi) OR (hanh vi)) ca tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (thu sach)) ty xang xa hoi. hieu kem cau luc ngan ((hang vi) or (hanh vi)) ca tren".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) OR (thu sach)) ty xang xa hoi. hieu kem cau luc ngan ((hang vi) or (hanh vi)) ca tren*.