Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
hieu van » hieu va, thien van, lieu va
danh dau » lanh dao, hang dau, danh tu
danh dai » danh di, danh sai, vanh dai
truc va » thuc va, thuc vat, trung va
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.

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