Perhaps you should try some spelling variations:
sach hoi » sach doi, sach moi, cach thoi
sach bai » sach dao, cac bai, sach xa
tan khoa » toan khoa, tran khoa, san khoa
khoa hoc » hoa hoc
gian dan » gian lang
cuu mon » cuu mo, cuu mot, cuu cong
mon hoc » toan hoc, dong hoc
hoc tan » hoc tang, hoc dan, hoc tap
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 hoi) or (sach bai)) tap, nghien cuu mon hoc tan khoa hoc xa hoi va gian dan~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc ((sach hoi) OR (sach bai)) tap, nghien cuu mon hoc tan khoa hoc xa hoi va gian dan.
• Adding a wildcard symbol may retrieve word variants: toc ((sach hoi) or (sach bai)) tap, nghien cuu mon hoc tan khoa hoc xa hoi va gian dan*.