Perhaps you should try some spelling variations:
nganh dang » ngan hang, nhan dang, nganh cong
dang thuoc » dung thuoc
sach doi » sach hoi, sach moi, sach dao
toan hoc » toan khoa, van hoc, hoa hoc
dong hoc » dong co, dong luc
thuoc ma » hoc ma, duoc ma
nhan dan » phan dau, gian dan, nhan tai
tu sach » thu sach, su sach, te sach
doi tap » doi tac, doi dap, doi tai
va nhan » van nhan, ca nhan, va phan
ma hoi » mai hoi, xa hoi, ma hoa

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 tap, nghien cuu ((toan hoc) or (dong hoc)) nganh dang thuoc ma hoi va nhan dan~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach doi tap, nghien cuu ((toan hoc) OR (dong hoc)) nganh dang thuoc ma hoi va nhan dan.
• Adding a wildcard symbol may retrieve word variants: tu sach doi tap, nghien cuu ((toan hoc) or (dong hoc)) nganh dang thuoc ma hoi va nhan dan*.