Perhaps you should try some spelling variations:
doanh khoa » toan khoa
thanh van » thanh san, thanh toan, thanh phan
sach hoc » cach hoc, sach hoi, mach hoc
cuu tong » cuu cong, cuu tinh, huu tung
co doanh » cho doanh, cao doanh, so doanh
khoa hoc » hoa hoc
hang tai » hang va, dung tai
su sach » so sach, vu sach
tong co » tong cot, trong co, thong co
ha van » hoa van, nha van, va van
ma ha » ma hoa, mai ha, my ha

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach hoc tap, nghien cuu tong co doanh khoa hoc ma ha van ((thanh van) or (hang tai))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach hoc tap, nghien cuu tong co doanh khoa hoc ma ha van ((thanh van) OR (hang tai)).
• Adding a wildcard symbol may retrieve word variants: su sach hoc tap, nghien cuu tong co doanh khoa hoc ma ha van ((thanh van) or (hang tai))*.