Perhaps you should try some spelling variations:
nghien cac » nghiep cach, nghien cuu, nghiep cay
doanh khoa » toan khoa
cong toan » cong tan, cong hoan, cong tuan
cac tong » cac tuong, bac tong, cac dong
tong tap » tuong tac, trong tan, cong tac
cac cong » cua cong
khoa hoc » hoa hoc
mai khoi » mai khoa, tai khoa, cac khoi
nhan tai » hang tai, van tai, toan tai
mai hoi » dai hoi, lai hoi, mai doi
va nhan » van nhan, ca nhan, va phan

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 tong tap, nghien cac cong toan doanh khoa hoc ((mai hoi) or (mai khoi)) va nhan tai~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu cac tong tap, nghien cac cong toan doanh khoa hoc ((mai hoi) OR (mai khoi)) va nhan tai.
• Adding a wildcard symbol may retrieve word variants: tu cac tong tap, nghien cac cong toan doanh khoa hoc ((mai hoi) or (mai khoi)) va nhan tai*.