Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
nhung cong » dung cong, hang cong, nhung don
thong cong » trong cong, tong cong, thong thong
hoc hieu » hoc thieu, hoc hien, doc hieu
hanh han » hanh nhan, hanh phan, hanh san
toan tai » toan tap, doanh tai, toan cao
toan ban » van ban
han va » hang va, hanh va, nhan va

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: hoc hieu quang - hanh han va ((nhung cong) OR (thong cong)) dan ((toan tai) OR (toan ban))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc hieu quang - hanh han va ((nhung cong) OR (thong cong)) dan ((toan tai) or (toan ban))~".
• Adding a wildcard symbol may retrieve word variants: hoc hieu quang - hanh han va ((nhung cong) OR (thong cong)) dan ((toan tai) or (toan ban))*.