Perhaps you should try some spelling variations:
khong thong » thong thong, khong trong, thong thuong
hieu quang » thieu quang, hieu quan, hieu qua
doanh khoa » toan khoa
theo hieu » theo chieu, theo tieu, thien hieu
doanh hua » doanh cua, doanh ha, doanh luan
tran van » luan van
san van » tan van, luan van, dang van

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

• Performing a fuzzy search may retrieve terms with similar spellings: theo hieu quang - hanh ((doanh hua) or (doanh khoa)) khong thong ((san van) OR (tran van)) tai~.
• If you are trying to use Boolean operators, they must be ALL CAPS: theo hieu quang - hanh ((doanh hua) OR (doanh khoa)) khong thong ((san van) OR (tran van)) tai*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "theo hieu quang - hanh ((doanh hua) or (doanh khoa)) khong thong ((san van) OR (tran van)) tai*".