Perhaps you should try some spelling variations:
thanh hoi » thanh hoai, thanh hoa, thanh hai
dan thanh » dang thanh, danh thanh, ban thanh
toc sach » doc sach, thuoc sach, nuoc sach
hoc sach » hoc sinh, hoc cac, hoc anh
thuc dan » thuc hanh, hoc dan, thuc vat
nam thuc » nam thuoc, am thuc, nam thu
hieu van » hieu va, thien van, lieu va
hoi cua » hoi chuc
ky tang » ky nang, ky dang, kho tang
ky lang » ky nang, ky dang, tay lang
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: ((toc sach) OR (hoc sach)) ((ky lang) or (ky tang)) xa hoi. hieu van nam thuc dan thanh hoi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc sach)) ((ky lang) OR (ky tang)) xa hoi. hieu van nam thuc dan thanh hoi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (hoc sach)) ((ky lang) or (ky tang)) xa hoi. hieu van nam thuc dan thanh hoi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) OR (hoc sach)) ((ky lang) or (ky tang)) xa hoi. hieu van nam thuc dan thanh hoi cua tre*.