Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
sach dao » lanh dao
tan khoa » toan khoa, tran khoa, san khoa
khoa hoc » hoa hoc
nhan dan » phan dau, gian dan
nhan tai » hang tai, van tai, toan tai
dao tap » dao tao, dao tay, dao gap
hoc tan » hoc tang, hoc dan, hoc tap
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: doc sach dao tap, nghien cuu mo hoc tan khoa hoc ma hoi va ((nhan dan) or (nhan tai))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach dao tap, nghien cuu mo hoc tan khoa hoc ma hoi va ((nhan dan) OR (nhan tai)).
• Adding a wildcard symbol may retrieve word variants: doc sach dao tap, nghien cuu mo hoc tan khoa hoc ma hoi va ((nhan dan) or (nhan tai))*.