Perhaps you should try some spelling variations:
mach hoc » cach hoc, dich hoc, anh hoc
cuu tong » cuu cong, cuu tinh, huu tung
so doanh » so danh, su doanh, hoa doanh
toan hoc » toan khoa, van hoc, tin hoc
nhan dan » phan dau, gian dan, nhan tai
su mach » su sach
tong so » tuong so, thong so, tong son
va nhan » van nhan, ca nhan, va phan
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: su mach hoc tap, nghien cuu tong so doanh ((toan hoc) or (hoa hoc)) ma hoi va nhan dan~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su mach hoc tap, nghien cuu tong so doanh ((toan hoc) OR (hoa hoc)) ma hoi va nhan dan.
• Adding a wildcard symbol may retrieve word variants: su mach hoc tap, nghien cuu tong so doanh ((toan hoc) or (hoa hoc)) ma hoi va nhan dan*.