Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
nhung cong » thong cong, hang cong, nhung don
hanh tinh » hanh trinh, nhanh tinh, thanh tinh
dung cong » dung trong
hoc hieu » hoc thieu, hoc hien, doc hieu
dan phan » doan phan, dan chan, van phan
phan cau » phan dau, phan cac, phan tu
tinh va » tich va, trinh van, trinh vat

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc hieu quang - hanh tinh va ((nhung cong) or (dung cong)) dan phan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc hieu quang - hanh tinh va ((nhung cong) OR (dung cong)) dan phan cau.
• Adding a wildcard symbol may retrieve word variants: hoc hieu quang - hanh tinh va ((nhung cong) or (dung cong)) dan phan cau*.