Perhaps you should try some spelling variations:
sach doi » sach hoi, sach moi, sach dao
dan khoa » dang khoa, san khoa, van khoa
su sach » so sach, vu sach
doi tap » doi tac, doi dap, doi tai
dap tan » dac tan, dai tan, tap toan
tan van » tran van, tang van, luan van
cuu mo » cuu mot, cuu ho, cuu ma
mo hoc » mon hoc, co hoc
hoc xa » hoc ma

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

• If you are trying to use Boolean operators, they must be ALL CAPS: su sach doi tap, nghien cuu mo hoc ((dan khoa) OR (da khoa)) hoc xa hoi dap tan van~.
• Adding a wildcard symbol may retrieve word variants: su sach doi tap, nghien cuu mo hoc ((dan khoa) or (da khoa)) hoc xa hoi dap tan van*.