Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
hau thuc » huu thuc, ha thuc, mau thuc
ty dang » ty xang, ty hang, ty dong
ky dang » ky nang, ky danh
van hau » van ha, van hai, van dau
thuc va » thuc vat, thuc dan, thuc day
va tinh » may tinh
tai cua » thai cua, tai cuc, dai 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 ((ty dang) OR (ky dang)) xa hoi. hieu van hau thuc va tinh ((tai cua) or (tri cua)) te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((ty dang) OR (ky dang)) xa hoi. hieu van hau thuc va tinh ((tai cua) OR (tri cua)) te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((ty dang) OR (ky dang)) xa hoi. hieu van hau thuc va tinh ((tai cua) or (tri cua)) te".
• Adding a wildcard symbol may retrieve word variants: toc sach ((ty dang) OR (ky dang)) xa hoi. hieu van hau thuc va tinh ((tai cua) or (tri cua)) te*.