Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
hieu lang » chieu sang, nhieu tang, hieu van
trinh han » trinh quan
ban cong » bang cong, van cong, phan cong
cong dan » cong san, cong tan, huong dan
dan toan » van toan, dan than, manh toan
toan tap » toan ban

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

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