Perhaps you should try some spelling variations:
nghien huu » nghien cuu, nguyen huu, nhiem huu
toc sach » hoc sach, doc sach, thuoc sach
sach hoc » cach hoc, sach hoi, mach hoc
hoc tang » hoc bang, hoc tieng, hoc trong
khoa hoc » hoa hoc
nhan dan » phan dau, gian dan, nhan tai
huu mot » cuu mot, huy mot, hieu mot
hoc tan » hoc dan, hoc tai, hoc can
hoc xa » hoc ma
hoi ca » hoi cua, hoi cac, hoi cau

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 hoc tap, nghien huu mot ((hoc tan) or (hoc tang)) khoa hoc xa hoi ca nhan dan~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach hoc tap, nghien huu mot ((hoc tan) OR (hoc tang)) khoa hoc xa hoi ca nhan dan.
• Adding a wildcard symbol may retrieve word variants: toc sach hoc tap, nghien huu mot ((hoc tan) or (hoc tang)) khoa hoc xa hoi ca nhan dan*.