Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
hieu va » hieu qua
thuc va » thuc vat, thuc dan, thuc day
dan vai » dan va, dan tai, dan vat
cuu tre » cau tren, cau treo
cua tre » cua te, cua triet, dua tren
va dan » ca dan, va dao, va dau

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