Perhaps you should try some spelling variations:
hieu manh » chieu xanh, hieu nganh, dieu hanh
hieu lang » chieu sang, hieu quang, nhieu tang
chinh cua » chinh ca, chinh sua, chinh luan
hinh cua » sinh cua, tinh cua, dinh cua
cong bai » cuong bai, cong hai, cung bai
bai toan » bai tap
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: hoc ((hieu manh) or (hieu lang)) - hanh ((chinh cua) OR (hinh cua)) trong cong bai toan ban~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((hieu manh) OR (hieu lang)) - hanh ((chinh cua) OR (hinh cua)) trong cong bai toan ban.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((hieu manh) or (hieu lang)) - hanh ((chinh cua) OR (hinh cua)) trong cong bai toan ban".
• Adding a wildcard symbol may retrieve word variants: hoc ((hieu manh) or (hieu lang)) - hanh ((chinh cua) OR (hinh cua)) trong cong bai toan ban*.