Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
tinh va » tich va, trinh van, trinh vat
tinh da » tinh gia, tinh lao, tinh nam
van cac » van hac, van cau, van bac
ty dang » ky dang, ty hang, ty dong
mam hoi » mam hoai, nam hoi, mai hoi
cua tre » cua te, cuu tre, cua triet
cac tu » cac thu, cach tu, cac du

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 ((ty dang) OR (ty xang)) mam hoi. hieu van cac tu va ((tinh da) or (tinh va)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((ty dang) OR (ty xang)) mam hoi. hieu van cac tu va ((tinh da) OR (tinh va)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((ty dang) OR (ty xang)) mam hoi. hieu van cac tu va ((tinh da) or (tinh va)) cua tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ((ty dang) OR (ty xang)) mam hoi. hieu van cac tu va ((tinh da) or (tinh va)) cua tre*.