Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
xang xay » dang xay, xang dau, cong xay
va triet » va thiet, va trien, ve triet
sach ty » sach y, sach tu, sach thu
hieu ve » hieu va, hieu van
tinh ve » trinh ve, tinh ven, dinh ve
ve cam » ve cham, ve cac, va cam
tuc va » thuc va, truc va, tuc xa
ve va » ve van, te va, ke va

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 ty ((xang xay) OR (van xay)) hoi. hieu ve cam ((tuc va) or (duc va)) tinh ve va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ty ((xang xay) OR (van xay)) hoi. hieu ve cam ((tuc va) OR (duc va)) tinh ve va triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ty ((xang xay) OR (van xay)) hoi. hieu ve cam ((tuc va) or (duc va)) tinh ve va triet".
• Adding a wildcard symbol may retrieve word variants: toc sach ty ((xang xay) OR (van xay)) hoi. hieu ve cam ((tuc va) or (duc va)) tinh ve va triet*.