Perhaps you should try some spelling variations:
thanh doi » thanh loi, thanh moi, thanh do
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
thuc day » thuc dan
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
cua tre » cua te, cua triet, dua tren
cuu tre » cau tren, cau treo

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 xa hoi. hieu van nam ((thuc day) OR (thuc vat)) thanh doi ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky nang xa hoi. hieu van nam ((thuc day) OR (thuc vat)) thanh doi ((cua tre) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky nang xa hoi. hieu van nam ((thuc day) OR (thuc vat)) thanh doi ((cua tre) or (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: toc sach ky nang xa hoi. hieu van nam ((thuc day) OR (thuc vat)) thanh doi ((cua tre) or (cuu tre))*.