Perhaps you should try some spelling variations:
hoc doanh » hoa doanh, hoc danh, hoc dan
doanh hoa » doanh khoa, doanh hoan, danh hoa
toc sach » hoc sach, doc sach, thuoc sach
sach hoi » sach doi, sach moi, cach thoi
nhan dan » phan dau, gian dan
nhan tai » hang tai, van tai, toan tai
mo hoc » mon hoc, co hoc
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: toc sach hoi dap, nghien cuu mo hoc doanh hoa hoc ma hoi va ((nhan dan) or (nhan tai))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach hoi dap, nghien cuu mo hoc doanh hoa hoc ma hoi va ((nhan dan) OR (nhan tai)).
• Adding a wildcard symbol may retrieve word variants: toc sach hoi dap, nghien cuu mo hoc doanh hoa hoc ma hoi va ((nhan dan) or (nhan tai))*.