Perhaps you should try some spelling variations:
ban hanh » ban hang
toc sach » hoc sach, doc sach, thuoc sach
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
sang cho » danh cho, dung cho, sang tao
cac vuc » cac vung, cac cuoc, cac quoc
hieu ve » hieu va, hieu van
cho hoc » co hoc, khoa hoc
ty sang » ty xang, ty hang, duy sang
vi cua » vai cua, di cua

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((te sach) OR (toc sach)) ty sang cho hoc. hieu ve ((cac vuc) or (cac nuoc)) ban hanh vi cua cac~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ty sang cho hoc. hieu ve ((cac vuc) OR (cac nuoc)) ban hanh vi cua cac*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) OR (toc sach)) ty sang cho hoc. hieu ve ((cac vuc) or (cac nuoc)) ban hanh vi cua cac*".