Perhaps you should try some spelling variations:
sach doi » sach hoi, sach moi, sach dao
dan khoa » dang khoa, da khoa, san khoa
cau nhan » chau nhan, ca nhan, cam nhan
su sach » so sach, vu sach
doi dap » hoi dap, doi dau, do dap
cuu hoa » cuu khoa, cuu hoan, cau hoa
xa khoa » da khoa, bia khoa, tai khoa
cu nhan » ca nhan
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: su sach doi dap, nghien cuu hoa hoc dan khoa hoc xa khoa ((cau nhan) or (cu nhan)) dan~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach doi dap, nghien cuu hoa hoc dan khoa hoc xa khoa ((cau nhan) OR (cu nhan)) dan.
• Adding a wildcard symbol may retrieve word variants: su sach doi dap, nghien cuu hoa hoc dan khoa hoc xa khoa ((cau nhan) or (cu nhan)) dan*.