Perhaps you should try some spelling variations:
thiet tach » chiet tach, thien hach, thuat tach
trung phan » trung thanh, trung ha, trung tuan
hoc thiet » hoc thieu, hoc thuyet, hoc hien
dung phan » dung nhan, dung luan, dung ha
cong toan » cong hoan, cong tuan, cong doan
cong tan » cong tac, cong san, cong thanh
phan tap » phan lap, han tap, pha tap

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 - hanh ((trung phan) or (dung phan)) xuong ((cong toan) OR (cong tan)) phan tap~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc thiet tach - hanh ((trung phan) OR (dung phan)) xuong ((cong toan) OR (cong tan)) phan tap.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc thiet tach - hanh ((trung phan) or (dung phan)) xuong ((cong toan) OR (cong tan)) phan tap".
• Adding a wildcard symbol may retrieve word variants: hoc thiet tach - hanh ((trung phan) or (dung phan)) xuong ((cong toan) OR (cong tan)) phan tap*.