Perhaps you should try some spelling variations:
sach doi » sach hoi, sach moi, sach dao
tu sach » thu sach, su sach, te sach
doi tac » dong tac
cuu mon » cuu mo, cuu mot, cuu cong
mon hoc » toan hoc, dong hoc
va nhan » van nhan, ca nhan, va phan
nhan va » nhan tai, nhan dan, nhan tao
hoc xa » hoc ma
toan » tran

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 doi tac, nghien cuu mon hoc ((doanh khoa) or (toan khoa)) hoc xa hoi va nhan va~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach doi tac, nghien cuu mon hoc ((doanh khoa) OR (toan khoa)) hoc xa hoi va nhan va.
• Adding a wildcard symbol may retrieve word variants: tu sach doi tac, nghien cuu mon hoc ((doanh khoa) or (toan khoa)) hoc xa hoi va nhan va*.