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
ve pham » v pham, ve phan, ve phat
va xanh » va danh, va hanh, va anh
xanh di » danh di, vanh dai, xanh tai
cua tre » cua te, cuu tre, cua triet
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: ((te sach) or (doc sach)) ky tang ma hoi. hieu ((ve pham) OR (vi pham)) duc va xanh di 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) OR (vi pham)) duc va xanh di 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) OR (vi pham)) duc va xanh di cua tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (doc sach)) ky tang ma hoi. hieu ((ve pham) OR (vi pham)) duc va xanh di cua tre*.