Perhaps you should try some spelling variations:
cach thoi » cac thoi, cach thuc, cach noi
nhan dann » nhan dang, phan dang, nhac dan
thoi dap » hoi dap, thoi dai, thi dap
cuu toan » cuu hoan, cua toan, huu toan
toan hoc » toan khoa, van hoc, hoa hoc
dan khoa » dang khoa, da khoa, san khoa
khoa hoc » hoa hoc
nhan dan » phan dau, gian dan, nhan tai
tu cach » tu cac
hoc cau » hoc cao, hoc cac, hoc can
hoc xa » hoc ma
xa hoc » xa hoi, va hoc, xa hoa

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 dap, nghien cuu toan hoc dan khoa hoc xa hoc cau ((nhan dann) or (nhan dan))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu cach thoi dap, nghien cuu toan hoc dan khoa hoc xa hoc cau ((nhan dann) OR (nhan dan)).
• Adding a wildcard symbol may retrieve word variants: tu cach thoi dap, nghien cuu toan hoc dan khoa hoc xa hoc cau ((nhan dann) or (nhan dan))*.