Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
va triet » va thiet, va trien, ve triet
ky dung » ly dung, ky dang, ky vung
hieu ve » hieu va, hieu van
luc van » luoc van, luu van, duc van
hanh tu » anh tu, danh tu
va hoi » xa hoi, va hoc, va hoa
ve cau » ke cau, va cau, ve cac
luan » quan, lan

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)) ky dung va hoi. hieu ve cau ((luc van) or (luan van)) hanh tu va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ky dung va hoi. hieu ve cau ((luc van) OR (luan van)) hanh tu va triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) OR (toc sach)) ky dung va hoi. hieu ve cau ((luc van) or (luan van)) hanh tu va triet".
• Adding a wildcard symbol may retrieve word variants: ((te sach) OR (toc sach)) ky dung va hoi. hieu ve cau ((luc van) or (luan van)) hanh tu va triet*.