Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
trung phai » trung phan, trung phat, truong phan
nhung cong » dung cong, thong cong, hang cong
trung hai » trung ha, trung dai, trong hai
doc hieu » toc thieu, hoc thieu, hoc hien
cong tan » cong tac, cong san, cong thanh
than tap » toan tap, han tap, than cap
phan tap » phan lap, han tap, pha tap

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 - thanh ((trung phai) or (trung hai)) nhung cong tan ((than tap) OR (phan tap))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu quang - thanh ((trung phai) OR (trung hai)) nhung cong tan ((than tap) OR (phan tap)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc hieu quang - thanh ((trung phai) or (trung hai)) nhung cong tan ((than tap) OR (phan tap))".
• Adding a wildcard symbol may retrieve word variants: doc hieu quang - thanh ((trung phai) or (trung hai)) nhung cong tan ((than tap) OR (phan tap))*.