Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hieu van » thien van, lieu va, hieu ve
sach ty » sach y, sach tu, sach thu
ty nang » ky nang, ty xang, ty hang
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va, hieu qua
cac dat » cac dan, cai dat, cac dai
va hanh » van hanh, va thanh, ban hanh
va danh » va dinh, va dan, dia danh
ma hoi » mai hoi, xa hoi, ma hoa
di cua » dai cua, doi cua, de cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ty nang ma hoi. ((hieu van) or (hieu va)) cac dat ((va hanh) OR (va danh)) di cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ty nang ma hoi. ((hieu van) OR (hieu va)) cac dat ((va hanh) OR (va danh)) di cua vat.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ty nang ma hoi. ((hieu van) or (hieu va)) cac dat ((va hanh) OR (va danh)) di cua vat".
• Adding a wildcard symbol may retrieve word variants: thu sach ty nang ma hoi. ((hieu van) or (hieu va)) cac dat ((va hanh) OR (va danh)) di cua vat*.