Perhaps you should try some spelling variations:
sach tham » sach nha
hieu cac » hieu luc, hieu van, vien cac
danh vai » danh sai, danh va, doanh van
vai cua » dai cua, hai cua, lai cua
va danh » va dinh, va dan, va hanh
hieu va » lieu va, hieu qua
tu sach » thu sach, su sach, te sach
nang xa » nang x, lang xa, mang xa
nang ma » tang ma, sang ma, nang cao
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: tu sach tham ((nang xa) OR (nang ma)) hoi. hieu ((hieu cac) or (hieu va)) nuoc va danh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach tham ((nang xa) OR (nang ma)) hoi. hieu ((hieu cac) OR (hieu va)) nuoc va danh vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach tham ((nang xa) OR (nang ma)) hoi. hieu ((hieu cac) or (hieu va)) nuoc va danh vai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach tham ((nang xa) OR (nang ma)) hoi. hieu ((hieu cac) or (hieu va)) nuoc va danh vai cua tre*.