Perhaps you should try some spelling variations:
sach tham » sach nha
toc sach » hoc sach, doc sach, thuoc sach
va hang » van hang, va nang, va lang
truc va » thuc va, thuc vat, trung va
va cham » va chat, va tham
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
cua tre » cua te, cuu tre, cua triet
va cam » va cac, va cao, va cai
va cua » va chua, via cua, ca cua

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

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