Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
nay thuc » nam thuc, cay thuc, day thuc
cau tren » cu tren, dau tren, ca tren
hoc sach » hoc sinh, hoc cac, hoc anh
dan vai » dan va, dan tai, dan vat
thuc va » thuc vat, thuc dan, thuc day
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
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 sach) or (hoc sach)) ky lang xa hoi. hieu va nay thuc va dan vai ((cau tren) or (cua tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc sach)) ky lang xa hoi. hieu va nay thuc va dan vai ((cau tren) OR (cua tre)).
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (hoc sach)) ky lang xa hoi. hieu va nay thuc va dan vai ((cau tren) or (cua tre))*.