Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
khoa hoc » hoa hoc
van hanh » van thanh, ban hanh, van anh
sach vu » sach va, sach tu, sach uu
hieu va » lieu va, hieu qua
cac duc » cac du, cao duc, cac dac
duc van » duc va, duc tan, duc manh
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: toc sach vu ngan ((((cho hoc) OR (khoa hoc))) or (co hoc)). hieu va cac duc van hanh vi cua cac~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach vu ngan ((((cho hoc) OR (khoa hoc))) OR (co hoc)). hieu va cac duc van hanh vi cua cac*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach vu ngan ((((cho hoc) OR (khoa hoc))) or (co hoc)). hieu va cac duc van hanh vi cua cac*".