Perhaps you should try some spelling variations:
quang tranh » quang thanh, quang tran, quang trach
thiet hach » thien hach, thuyet hach, thiet hai
thong cong » trong cong, tong cong, thong thong
hoc thiet » hoc thieu, hoc thuyet, hoc hien
dung cong » dung trong
tranh ban » trinh ban, tranh hang, tranh luan
tranh va » tranh van, trang va, trinh va

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc thiet hach - canh tranh va ((thong cong) or (dung cong)) quang tranh ban~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc thiet hach - canh tranh va ((thong cong) OR (dung cong)) quang tranh ban.
• Adding a wildcard symbol may retrieve word variants: hoc thiet hach - canh tranh va ((thong cong) or (dung cong)) quang tranh ban*.