Perhaps you should try some spelling variations:
chieu sach » chinh sach, chiet tach, chieu sang
canh manh » lanh manh, canh tranh, cach mang
trong bai » trong ban, thong bai, trong hai
chi sach » chinh sach, co sach, moi sach
cua rung » cua trung, cua rang, cua truong
cua dong » chua dong, cua cong, cua dang
bai toan » bai tap
toan cau » toan cao, toan ban, toan tap

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

• Performing a fuzzy search may retrieve terms with similar spellings: doi ((chi sach) or (chieu sach)) - canh manh ((cua rung) or (cua dong)) trong bai toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doi ((chi sach) OR (chieu sach)) - canh manh ((cua rung) OR (cua dong)) trong bai toan cau.
• Adding a wildcard symbol may retrieve word variants: doi ((chi sach) or (chieu sach)) - canh manh ((cua rung) or (cua dong)) trong bai toan cau*.