Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
cau tren » cu tren, dau tren, ca tren
ky dang » ky nang, ky danh
hieu ha » hieu hoa, hieu va, hieu xa
hieu ca » hieu cac, hieu cua, hieu va
ky tang » ky nang, kho tang, ky trong
thuc ca » thuc cua, thuc can, thuc cao
dan vai » dan va, dan tai, dan vat
vai cau » va cau, van cau, vai cac
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: toc sach ((ky tang) or (ky dang)) xa hoi. ((hieu ha) or (hieu ca)) nam thuc ca dan vai cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((ky tang) OR (ky dang)) xa hoi. ((hieu ha) OR (hieu ca)) nam thuc ca dan vai cau tren.
• Adding a wildcard symbol may retrieve word variants: toc sach ((ky tang) or (ky dang)) xa hoi. ((hieu ha) or (hieu ca)) nam thuc ca dan vai cau tren*.