Perhaps you should try some spelling variations:
doanh hoa » doanh khoa, doanh hoan, danh hoa
mach hoc » cach hoc, dich hoc, anh hoc
cuu tong » cuu cong, cuu tinh, huu tung
so doanh » so danh, su doanh, hoa doanh
van nhan » van phan, van thanh, danh nhan
su mach » su sach
tong so » tuong so, thong so, tong son
va nhan » ca nhan, va phan, va nha
ma hoi » mai hoi, xa hoi, ma hoa

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: su mach hoc tap, nghien cuu tong so doanh hoa hoc ma hoi ((va nhan) OR (van nhan)) dan~.
• Adding a wildcard symbol may retrieve word variants: su mach hoc tap, nghien cuu tong so doanh hoa hoc ma hoi ((va nhan) or (van nhan)) dan*.