Perhaps you should try some spelling variations:
hanh trinh » canh tranh, hanh chinh
chieu sang » chieu sach, chieu xanh, nhieu tang
nhung cong » dung cong, hang cong, nhung don
thong cong » trong cong, tong cong, thong thong
hieu lang » hieu quang, nhieu tang, hieu van
trinh va » trinh van, trinh vat, trinh ve
san toan » van toan, dan toan, manh 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: hoc ((chieu sang) OR (hieu lang)) - hanh trinh va ((nhung cong) or (thong cong)) san toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((chieu sang) OR (hieu lang)) - hanh trinh va ((nhung cong) OR (thong cong)) san toan cau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((chieu sang) OR (hieu lang)) - hanh trinh va ((nhung cong) or (thong cong)) san toan cau".
• Adding a wildcard symbol may retrieve word variants: hoc ((chieu sang) OR (hieu lang)) - hanh trinh va ((nhung cong) or (thong cong)) san toan cau*.