Perhaps you should try some spelling variations:
sach hoi » sach doi, sach moi, cach thoi
dan khoa » dang khoa, da khoa, san khoa
khoa hoc » hoa hoc
nhan dan » phan dau, gian dan, nhan tai
tu sach » thu sach, su sach, te sach
cuu mon » cuu mo, cuu mot, cuu cong
mon hoc » toan hoc, dong hoc
hoi vau » hoi cau
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: tu sach hoi dap, nghien cuu mon hoc dan khoa hoc xa ((hoi va) or (hoi vau)) nhan dan~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach hoi dap, nghien cuu mon hoc dan khoa hoc xa ((hoi va) OR (hoi vau)) nhan dan.
• Adding a wildcard symbol may retrieve word variants: tu sach hoi dap, nghien cuu mon hoc dan khoa hoc xa ((hoi va) or (hoi vau)) nhan dan*.