Perhaps you should try some spelling variations:
nam thuoc » nam thuc, nam thu, nha thuoc
hoc sach » hoc sinh, hoc cac, hoc anh
dang xay » dang van, van xay
toc sac » toc sach, toc san, doc sach
vai cua » dai cua, hai cua, lai cua
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
xay hoi » xa hoi, tay hoi, cay phoi
ky dang » ky nang, ky danh
va dan » va dao, va dau, va dap
ca dan » cac dan, ca dao
va nam » van nam, ha nam, va nay

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 thuoc ((va dan) or (ca 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 thuoc ((va dan) OR (ca 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 thuoc ((va dan) or (ca dan)) vai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((toc sac) OR (hoc sach)) ky dang xay hoi. hieu va nam thuoc ((va dan) or (ca dan)) vai cua tre*.