Perhaps you should try some spelling variations:
thanh tung » thanh cong
nhung cong » thong cong, hang cong, nhung don
hieu sang » chieu sang, hieu lang, hieu quang
dung cong » dung trong
doc hieu » toc thieu, hoc thieu, hoc hien
tung cua » trung cua, tuong cua, dung cua
gian nan » gian dan, gian lan, gian van

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 sang - thanh tung cua ((nhung cong) or (dung cong)) dan gian nan~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu sang - thanh tung cua ((nhung cong) OR (dung cong)) dan gian nan.
• Adding a wildcard symbol may retrieve word variants: doc hieu sang - thanh tung cua ((nhung cong) or (dung cong)) dan gian nan*.