Perhaps you should try some spelling variations:
duong trong » dung trong
trong mach » trong cac, trong minh, trong anh
mach toan » manh toan, hach toan, mach tuan
ho chieu » theo chieu, hoc thieu, doi chieu
trinh ve » trinh va, trinh vi, trinh viet
trinh he » trinh han, trinh hoa, trinh thi
toan ban » van ban
doi chi » doi khi

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((ho chieu) or (doi chi)) xanh - hanh ((trinh ve) OR (trinh he)) duong trong mach toan ban~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((ho chieu) OR (doi chi)) xanh - hanh ((trinh ve) OR (trinh he)) duong trong mach toan ban.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((ho chieu) or (doi chi)) xanh - hanh ((trinh ve) OR (trinh he)) duong trong mach toan ban".
• Adding a wildcard symbol may retrieve word variants: ((ho chieu) or (doi chi)) xanh - hanh ((trinh ve) OR (trinh he)) duong trong mach toan ban*.