Perhaps you should try some spelling variations:
hieu lang » chieu sang, hieu quang, nhieu tang
trinh vat » trinh van, trinh luat, trinh han
bang cong » dang cong, bang song, hang cong
doc hieu » toc thieu, hoc thieu, hoc hien
cong tap » cuong tap, cong tac, cong tan
tap toan » tap doan, tap quan, bai toan
toan ban » van ban

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 lang - hanh ((trinh vat) OR (sinh vat)) bang cong tap toan ban~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc hieu lang - hanh ((trinh vat) OR (sinh vat)) bang cong tap toan ban".
• Adding a wildcard symbol may retrieve word variants: doc hieu lang - hanh ((trinh vat) OR (sinh vat)) bang cong tap toan ban*.