Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
chieu sang » chieu sach, chieu xanh, hieu lang
nhung cong » dung cong, thong cong, hang cong
hanh tinh » hanh trinh, nhanh tinh, thanh tinh
cua nhung » va nhung
tinh cua » trinh cua, sinh cua, tinh chat
tan toan » tan tran, van toan, dan toan
tap toan » tap doan, tap quan, bai toan

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: hai ((hieu quang) OR (chieu sang)) - hanh tinh cua nhung cong ((tan toan) OR (tap toan)) cau~.
• Adding a wildcard symbol may retrieve word variants: hai ((hieu quang) or (chieu sang)) - hanh tinh cua nhung cong ((tan toan) or (tap toan)) cau*.