Perhaps you should try some spelling variations:
sach doi » sach hoi, sach moi, sach dao
dan khoa » dang khoa, da khoa, san khoa
te sach » toc sach
doi dap » hoi dap, doi dau, do dap
cuu mon » cuu mo, cuu mot, cuu cong
mon hoc » toan hoc, dong hoc
va phan » van phan, va phat, va phap
phan va » phan van, nhan va, han va

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach doi dap, nghien cuu mon hoc dan khoa ((hoc xa) or (hoc ma)) hoi va phan va~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach doi dap, nghien cuu mon hoc dan khoa ((hoc xa) OR (hoc ma)) hoi va phan va.
• Adding a wildcard symbol may retrieve word variants: te sach doi dap, nghien cuu mon hoc dan khoa ((hoc xa) or (hoc ma)) hoi va phan va*.