Perhaps you should try some spelling variations:
doc sach » toc sach, nuoc sach, dac sac
hoc sach » hoc sinh, hoc cac, hoc anh
nam thuc » nam thuoc, am thuc, nam thu
vai cua » dai cua, hai cua, lai cua
dan vai » dan va, dan tai, dan vat
thuc va » thuc vat, thuc dan, thuc day
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
ky dang » ky nang, ky danh
ky lang » ky nang, ky tang, tay lang
va nam » van nam, ha nam, va nay
va dan » ca dan, va dao, va dau
ha hoi » hoa hoi, ha noi, xa hoi

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

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