Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cau treo » cau theo, cau tren, cau triet
ky lang » ky nang, ky dang, tay lang
ky tang » ky nang, ky dang, kho tang
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 lang) OR (ky tang)) xa hoi. hieu ((van nam) or (ha nam)) thuc ca dan vai cau treo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((ky lang) OR (ky tang)) xa hoi. hieu ((van nam) OR (ha nam)) thuc ca dan vai cau treo.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((ky lang) OR (ky tang)) xa hoi. hieu ((van nam) or (ha nam)) thuc ca dan vai cau treo".
• Adding a wildcard symbol may retrieve word variants: toc sach ((ky lang) OR (ky tang)) xa hoi. hieu ((van nam) or (ha nam)) thuc ca dan vai cau treo*.