Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
te sach » toc sach
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 xanh » va danh, va hanh, va anh
ma hoi » mai hoi, xa hoi, ma hoa
di cua » doi cua, de cua, do 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 (doc sach)) ky tang ma hoi. hieu ve pham duc va xanh ((di cua) OR (dai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (doc sach)) ky tang ma hoi. hieu ve pham duc va xanh ((di cua) OR (dai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (doc sach)) ky tang ma hoi. hieu ve pham duc va xanh ((di cua) OR (dai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (doc sach)) ky tang ma hoi. hieu ve pham duc va xanh ((di cua) OR (dai cua)) tre*.