Perhaps you should try some spelling variations:
nay thuc » nam thuc, cay thuc, day thuc
dau tren » dau tien, dat tren, dau tieng
hoc sach » hoc sinh, hoc cac, hoc anh
toc sac » toc sach, toc san, doc sach
dan tai » van tai, dan thi, han tai
thuc va » thuc vat, thuc dan, thuc day
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
nang xa » nang x, lang xa, nang ma
va dan » ca dan, va dao, va dau
va nay » va ngay, va cay

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((toc sac) OR (hoc sach)) ky nang xa hoi. hieu va nay thuc va dan tai ((dau tren) or (cua tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sac) OR (hoc sach)) ky nang xa hoi. hieu va nay thuc va dan tai ((dau tren) OR (cua tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sac) OR (hoc sach)) ky nang xa hoi. hieu va nay thuc va dan tai ((dau tren) or (cua tre))".
• Adding a wildcard symbol may retrieve word variants: ((toc sac) OR (hoc sach)) ky nang xa hoi. hieu va nay thuc va dan tai ((dau tren) or (cua tre))*.