Perhaps you should try some spelling variations:
dong phuong » duong phuong, dong huong, dong thuong
dung phuong » dung thuong, bang phuong, dung chung
hieu quang » thieu quang, hieu quan, hieu qua
hanh tinh » hanh trinh, nhanh tinh, thanh tinh
doc hieu » toc thieu, hoc thieu, hoc hien
tinh cua » trinh cua, sinh cua, tinh chat
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 quang - hanh tinh cua ((dong phuong) or (dung phuong)) tinh toan tap~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu quang - hanh tinh cua ((dong phuong) OR (dung phuong)) tinh toan tap.
• Adding a wildcard symbol may retrieve word variants: doc hieu quang - hanh tinh cua ((dong phuong) or (dung phuong)) tinh toan tap*.