Perhaps you should try some spelling variations:
doanh trong » doanh tong, doanh thuong, dinh trong
nghien cua » nghien cuu, nghiep cua, nghiep vua
sach thoi » cach thoi, sach hoi, sach tham
cong toan » cong tan, cong hoan, cong tuan
trong hoc » truong hoc, tuong hoc, thong hoc
thoi tai » thoi dai, hoi tai, phoi tai
tai toan » tap toan, tai tuan, tam toan
bai toan » bai tap
so sach » so sanh, bo sach, co sach
hoc xa » hoc ma

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach thoi tai, nghien cua cong toan doanh trong hoc xa hoi ((tai toan) or (bai toan)) tai~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach thoi tai, nghien cua cong toan doanh trong hoc xa hoi ((tai toan) OR (bai toan)) tai.
• Adding a wildcard symbol may retrieve word variants: so sach thoi tai, nghien cua cong toan doanh trong hoc xa hoi ((tai toan) or (bai toan)) tai*.