Perhaps you should try some spelling variations:
nghien cac » nghiep cach, nghien cuu, nghiep cay
doanh khoa » toan khoa
cong toan » cong tan, cong tuan, cong doan
cong hoan » cong hoa, dong hoa, cong san
cac thoi » cac toi, cac hop, cac tro
thoi tap » toi tap, hoc tap, thoi dai
khoa hoc » hoa hoc
phan tai » pham tai, nhan tai, phan thi
va phan » van phan, va phat, va phap
ma hoi » mai hoi, xa hoi, ma hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu cac thoi tap, nghien cac ((cong toan) or (cong hoan)) doanh khoa hoc ma hoi va phan tai~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu cac thoi tap, nghien cac ((cong toan) OR (cong hoan)) doanh khoa hoc ma hoi va phan tai.
• Adding a wildcard symbol may retrieve word variants: tu cac thoi tap, nghien cac ((cong toan) or (cong hoan)) doanh khoa hoc ma hoi va phan tai*.