Perhaps you should try some spelling variations:
nghien huu » nghien cuu, nguyen huu, nhiem huu
hang khoa » dung khoa
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
hoc hang » hoc hanh, hoc bang, hoc tang
khoa hoc » hoa hoc
gian dan » gian lang
hoi tap » hoi dap, hoc tap, hoi tai
va gian » va gianh, van gian, va giai
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: ((toc sach) or (doc sach)) hoi tap, nghien huu co hoc hang khoa hoc xa hoi va gian dan~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) hoi tap, nghien huu co hoc hang khoa hoc xa hoi va gian dan.
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (doc sach)) hoi tap, nghien huu co hoc hang khoa hoc xa hoi va gian dan*.