Perhaps you should try some spelling variations:
dong phuong » duong phuong, dung phuong, dong thuong
hanh trinh » canh tranh, hanh chinh
dong huong » dong thuong, dong duong, cong huong
hieu sang » chieu sang, hieu quang, nhieu tang
hieu lang » chieu sang, hieu quang, nhieu tang
trinh cua » tinh cua, trinh luat, trinh quan
toan tap » toan ban

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc ((hieu sang) or (hieu lang)) - hanh trinh cua ((dong phuong) OR (dong huong)) tinh toan tap~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((hieu sang) OR (hieu lang)) - hanh trinh cua ((dong phuong) OR (dong huong)) tinh toan tap.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc ((hieu sang) or (hieu lang)) - hanh trinh cua ((dong phuong) OR (dong huong)) tinh toan tap".
• Adding a wildcard symbol may retrieve word variants: doc ((hieu sang) or (hieu lang)) - hanh trinh cua ((dong phuong) OR (dong huong)) tinh toan tap*.