Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
nam thuc » nam thuoc, am thuc, nam tu
dang xay » dang van, van xay
toc sac » toc sach, toc san, doc sach
vai cua » dai cua, hai cua, lai cua
dan vai » dan va, dan tai, dan vat
hieu va » lieu va, hieu qua
xay hoi » xa hoi, tay hoi, cay phoi
ky dang » ky nang, ky danh
cua tre » cua te, cuu tre, cua triet
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 sac) OR (hoc sach)) ky dang xay hoi. hieu va ((nam thuc) or (nam thu)) va dan vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sac) OR (hoc sach)) ky dang xay hoi. hieu va ((nam thuc) OR (nam thu)) va dan vai cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sac) OR (hoc sach)) ky dang xay hoi. hieu va ((nam thuc) or (nam thu)) va dan vai cua tre*".