Perhaps you should try some spelling variations:
thiet tach » chiet tach, thien hach, thuat tach
hoc thiet » hoc thieu, hoc thuyet, hoc hien
dung cong » dung trong
song ma » song xa, song da, song va
ma dung » mai dung, m dung, va dung
tan ran » tan tran, tan san, tan rao
tan van » tran van, tang van, luan van

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc thiet tach - nang song ma dung cong ((tan ran) or (tan van)) cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc thiet tach - nang song ma dung cong ((tan ran) OR (tan van)) cau.
• Adding a wildcard symbol may retrieve word variants: hoc thiet tach - nang song ma dung cong ((tan ran) or (tan van)) cau*.