Perhaps you should try some spelling variations:
trinh chuan » trinh quan, trinh luan, trinh phan
chieu sang » chieu sach, chieu xanh, hieu lang
nhung cong » dung cong, thong cong, hang cong
hieu sang » hieu lang, hieu quang, nhieu tang
trinh han » trinh quan
cong tinh » cong trinh, cong vinh, long tinh
tinh van » trinh van, dinh van, tinh va

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