Perhaps you should try some spelling variations:
cach thoi » cac thoi, cach thuc, cach noi
doanh hoa » doanh khoa, doanh hoan, danh hoa
thoi tap » toi tap, hoc tap, thoi dai
cuu cong » thu cong, cac cong
toan tai » toan tap, doanh tai, toan ban
tu cach » tu cac
hoc bai » hoc dai, hoc giai
bai hoi » bai choi, bai hoc, dai hoi
va toan » van toan, bai toan, tap toan

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

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