Perhaps you should try some spelling variations:
hoc sach » hoc cac, hoc anh
nam thuc » nam thuoc, am thuc, nam thu
vai cuu » vai cua
dan vai » dan va, dan tai, dan vat
thuc ca » thuc cua, thuc can, thuc cao
cuu tre » cua tre, cau tren, cau treo
hieu va » lieu va
dang xa » dang xay, lang xa, dang ha
ky dang » ky nang, ky danh
ca dan » cac dan, ca dao

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((hoc sach) OR (hoc sinh)) ky dang xa hoi. ((hieu va) or (hieu qua)) nam thuc ca dan vai cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((hoc sach) OR (hoc sinh)) ky dang xa hoi. ((hieu va) OR (hieu qua)) nam thuc ca dan vai cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((hoc sach) OR (hoc sinh)) ky dang xa hoi. ((hieu va) or (hieu qua)) nam thuc ca dan vai cuu tre".
• Adding a wildcard symbol may retrieve word variants: ((hoc sach) OR (hoc sinh)) ky dang xa hoi. ((hieu va) or (hieu qua)) nam thuc ca dan vai cuu tre*.