Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, diep quang
hanh trinh » canh tranh, hanh chinh
cong vang » cong lang, cong quang, cong ngang
trinh va » trinh van, trinh vat, trinh ve
cong van » cong san, song van, cong tan
toan cau » toan cao, toan ban, toan tap
va dung » van dung, va duong, vat dung

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc ((hieu quang) or (hieu qua)) - hanh trinh va dung ((cong van) OR (cong vang)) toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((hieu quang) OR (hieu qua)) - hanh trinh va dung ((cong van) OR (cong vang)) toan cau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((hieu quang) or (hieu qua)) - hanh trinh va dung ((cong van) OR (cong vang)) toan cau".
• Adding a wildcard symbol may retrieve word variants: hoc ((hieu quang) or (hieu qua)) - hanh trinh va dung ((cong van) OR (cong vang)) toan cau*.