Perhaps you should try some spelling variations:
hanh trinh » canh tranh, hanh chinh
hieu lang » chieu sang, hieu quang, nhieu tang
dung cong » dung trong
trinh va » trinh van, trinh vat, trinh ve
tap quan » tac quan, hai quan
bai toan » bai tap
ho hieu » ho chieu, hoi hieu, nho hieu
va dung » van dung, va duong, vat dung

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

• If you are trying to use Boolean operators, they must be ALL CAPS: ho hieu lang - hanh trinh va dung cong ((tap quan) OR (bai toan)) cau~.
• Adding a wildcard symbol may retrieve word variants: ho hieu lang - hanh trinh va dung cong ((tap quan) or (bai toan)) cau*.