Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
lang xa » lang ha, dang xay, lang van
cac tuc » cac toc, cac tu, cac tac
ky lang » ky nang, ky dang, ky tang
hieu va » lieu va, hieu qua
tuc va » thuc va, truc va, tuc xa
va dan » ca dan, va dao, va dau
va cua » va chua, via cua, ma cua
ca cua » co 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)) ky lang xa hoi. hieu va cac tuc va dan ((va cua) OR (ca cua)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ky lang xa hoi. hieu va cac tuc va dan ((va cua) OR (ca cua)) triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (toc sach)) ky lang xa hoi. hieu va cac tuc va dan ((va cua) OR (ca cua)) triet".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) ky lang xa hoi. hieu va cac tuc va dan ((va cua) OR (ca cua)) triet*.