Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
dinh dai » dinh dat, sinh dai, dinh dao
trung va » truong va, trang va, trung ha
van cham » van chat, van tham, va cham
sach ky » sac ky, sach y, sach ty
truc va » thuc va, thuc vat
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, me hoi

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