Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
nam thuc » nam thuoc, am thuc, nam thu
vat dan » va dan, van dan, vat ran
hieu va » hieu qua
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
huu tre » huu tri, cuu tre, huu them
dan va » doan va, dan ca, ban va
va huu » vu huu

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 (doc sach)) ky lang xa hoi. ((hieu va) or (lieu va)) nam thuc vat dan va huu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) ky lang xa hoi. ((hieu va) OR (lieu va)) nam thuc vat dan va huu tre.
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (doc sach)) ky lang xa hoi. ((hieu va) or (lieu va)) nam thuc vat dan va huu tre*.