Perhaps you should try some spelling variations:
nhuong cong » nhung cong, luong cong, duong cong
trung phai » trung phan, trung hai, truong phan
trung phat » truong phat, trong phat, trung phan
hieu xanh » chieu xanh, hieu manh, hieu nganh
hach toan » thanh toan, manh toan
doc hieu » toc thieu, hoc thieu, hoc hien
tac toan » tap toan, tam toan, tich toan

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

• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu xanh - thanh ((trung phai) OR (trung phat)) nhuong cong ((tac toan) OR (hach toan)) cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc hieu xanh - thanh ((trung phai) or (trung phat)) nhuong cong ((tac toan) OR (hach toan)) cau~".
• Adding a wildcard symbol may retrieve word variants: doc hieu xanh - thanh ((trung phai) or (trung phat)) nhuong cong ((tac toan) OR (hach toan)) cau*.