Perhaps you should try some spelling variations:
theo chieu » theo tieu, ho chieu, theo chu
chieu sach » chinh sach, chiet tach, chieu sang
nhung cong » dung cong, thong cong, hang cong
hanh tang » hanh trang, anh tang, hanh tung
hanh mang » nhanh mang, hanh trang, nhanh lang
cua nhung » va nhung
tap toan » tap quan, bai toan
tap doan » tap quan

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

• If you are trying to use Boolean operators, they must be ALL CAPS: theo chieu sach - ((hanh tang) OR (hanh mang)) cua nhung cong ((tap toan) OR (tap doan)) tap~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "theo chieu sach - ((hanh tang) or (hanh mang)) cua nhung cong ((tap toan) OR (tap doan)) tap~".
• Adding a wildcard symbol may retrieve word variants: theo chieu sach - ((hanh tang) or (hanh mang)) cua nhung cong ((tap toan) OR (tap doan)) tap*.