Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
hanh trinh » canh tranh, hanh chinh
hieu lang » chieu sang, nhieu tang, hieu van
trinh va » trinh van, trinh vat, trinh ve
cong dan » cong tan, huong dan, cong dong
cong san » cong tac
chan cau » phan cau, can cau, chinh cau

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

• The words AND, OR and NOT may confuse the search; try adding quotes: "doc ((hieu lang) OR (hieu quang)) - hanh trinh va nhung ((cong dan) OR (cong san)) chan cau~".
• Adding a wildcard symbol may retrieve word variants: doc ((hieu lang) OR (hieu quang)) - hanh trinh va nhung ((cong dan) OR (cong san)) chan cau*.