Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, diep quang
hanh trang » thanh trung, canh tranh, hanh trinh
cong ngang » cong nhan, cong quang, cong lang
ngang toan » nganh toan, dang toan, quang toan
toan ban » van ban
va hang » van hang, va nang, va hanh
va lang » va nang, hoa lang

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 trang ((va hang) or (va lang)) cong ngang toan ban~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((hieu quang) OR (hieu qua)) - hanh trang ((va hang) OR (va lang)) cong ngang toan ban.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((hieu quang) OR (hieu qua)) - hanh trang ((va hang) or (va lang)) cong ngang toan ban".
• Adding a wildcard symbol may retrieve word variants: hoc ((hieu quang) OR (hieu qua)) - hanh trang ((va hang) or (va lang)) cong ngang toan ban*.