Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
xanh tai » hanh tai, anh tai, vanh tai
trung va » truong va, trang va, trung ha
hieu van » hieu va, thien van, lieu va
truc va » thuc va, thuc vat
tai cua » thai cua, tai cuc, tri cua
van cau » van dau, van hau, van chat
sach ky » sac ky, sach y, sach ty
tang ma » mang may, tang van
nang ma » sang ma, nang cao, mang may
cua tre » cua te, cuu tre, cua triet

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

• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky ((nang ma) OR (tang ma)) hoi. hieu van cau ((truc va) OR (trung va)) xanh tai cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ky ((nang ma) OR (tang ma)) hoi. hieu van cau ((truc va) or (trung va)) xanh tai cua tre~".
• Adding a wildcard symbol may retrieve word variants: thu sach ky ((nang ma) OR (tang ma)) hoi. hieu van cau ((truc va) or (trung va)) xanh tai cua tre*.