Perhaps you should try some spelling variations:
thien hieu » thien nhien, thien chien, thien hue
hieu quan » hieu qua, lieu quan, thien quan
tran tuan » tran xuan, tran thanh, tranh luan
dung cong » dung trong
cong tap » cuong tap, cong tac, cong tan
tap toan » tap doan, tap quan, bai toan
toan cau » toan cao, toan ban, toan tap

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

• Performing a fuzzy search may retrieve terms with similar spellings: thien hieu quan - thanh ((tran tuan) or (tran quang)) dung cong tap toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thien hieu quan - thanh ((tran tuan) OR (tran quang)) dung cong tap toan cau.
• Adding a wildcard symbol may retrieve word variants: thien hieu quan - thanh ((tran tuan) or (tran quang)) dung cong tap toan cau*.