Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
thong cong » trong cong, tong cong, thong thong
hieu sang » chieu sang, hieu lang, nhieu tang
cong manh » cong danh, duong manh, cong thanh
manh toan » thanh toan, anh tuan, tinh toan
vang cua » mang cua, hang cua, tang cua
toan cau » toan cao, toan ban, toan tap
dan cua » dan ca, ban cua, dai cua

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

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