Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
thai cua » than cua, tai cuc, tri cua
ky tang » ky nang, ky dang, kho tang
tang ma » mang may, tang van
hieu ve » hieu va, hieu van
ve pham » vi pham, v pham, ve phan
va hanh » van hanh, va thanh, va danh
ma hoi » mai hoi, xa hoi, ma hoa

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 tang ma hoi. hieu ve pham duc va hanh ((thai cua) or (dai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ky tang ma hoi. hieu ve pham duc va hanh ((thai cua) OR (dai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) OR (toc sach)) ky tang ma hoi. hieu ve pham duc va hanh ((thai cua) or (dai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) OR (toc sach)) ky tang ma hoi. hieu ve pham duc va hanh ((thai cua) or (dai cua)) tre*.