Perhaps you should try some spelling variations:
chiet tach » chieu sach
chieu sang » chieu sach, chieu xanh, hieu lang
hang hang » nang hang, cang thang, hung thang
trong bai » trong ban, thong bai, trong hai
bai toan » bai tap
toan cau » toan cao, toan ban, toan tap
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: ho ((chiet tach) or (chieu sang)) - hang hang va dung trong bai toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ho ((chiet tach) OR (chieu sang)) - hang hang va dung trong bai toan cau.
• Adding a wildcard symbol may retrieve word variants: ho ((chiet tach) or (chieu sang)) - hang hang va dung trong bai toan cau*.