Perhaps you should try some spelling variations:
phuong thao » phuong thuc
hieu xanh » chieu xanh, hieu manh, hieu nganh
hanh tang » hanh trang, anh tang, hanh mang
doc hieu » toc thieu, hoc thieu, hoc hien
toan cau » toan cao, toan ban, toan tai
toan tap » toan ban
tang va » trang va, tang van, thang va
va dung » van dung, va duong, vat dung

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 xanh - hanh tang va dung ((phuong thao) or (phuong phap)) ((toan cau) or (toan tap))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu xanh - hanh tang va dung ((phuong thao) OR (phuong phap)) ((toan cau) OR (toan tap)).
• Adding a wildcard symbol may retrieve word variants: doc hieu xanh - hanh tang va dung ((phuong thao) or (phuong phap)) ((toan cau) or (toan tap))*.