Perhaps you should try some spelling variations:
nhung cong » dung cong, thong cong, hang cong
chieu sang » chieu sach, chieu xanh, nhieu tang
hieu lang » hieu quang, nhieu tang, hieu van
tranh vat » trinh vat, tranh va, tranh van
vat nhung » va nhung, vap nhung, vai nhung
van toan » van tan, van thanh, manh toan
van tuan » van quan, van ban, anh tuan

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 lang) or (chieu sang)) - canh tranh vat nhung cong ((van toan) OR (van tuan)) tap~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((hieu lang) OR (chieu sang)) - canh tranh vat nhung cong ((van toan) OR (van tuan)) tap.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((hieu lang) or (chieu sang)) - canh tranh vat nhung cong ((van toan) OR (van tuan)) tap".
• Adding a wildcard symbol may retrieve word variants: hoc ((hieu lang) or (chieu sang)) - canh tranh vat nhung cong ((van toan) OR (van tuan)) tap*.