Perhaps you should try some spelling variations:
nghien cac » nghiep cach, nghien cuu, nghiep cay
sach doi » sach hoi, sach moi, sach dao
cac cong » cua cong
cong hoc » dong hoc, cong hoa, cong coc
hoc danh » hoc dan, hoc anh, hoc hanh
danh hoa » thanh hoa, khanh hoa, nganh hoa
nhan dan » phan dau, gian dan, nhan tai
so sach » so sanh, bo sach, co sach
doi tap » doi tac, doi dap, doi tai
hoi dan » hoa dan, hoc dan, hoi dap
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: so sach doi tap, nghien cac cong hoc danh hoa hoc xa hoi dan ((nhan dan) or (dung tai))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach doi tap, nghien cac cong hoc danh hoa hoc xa hoi dan ((nhan dan) OR (dung tai)).
• Adding a wildcard symbol may retrieve word variants: so sach doi tap, nghien cac cong hoc danh hoa hoc xa hoi dan ((nhan dan) or (dung tai))*.