Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
cau treo » cau theo, cau tren, cau triet
ty hang » ly hang, ty xang, thi hang
ty nang » ky nang, ty xang, ly nang
thuc ca » thuc cua, thuc can, thuc cao
dan vai » dan va, dan tai, dan vat
vai cau » va cau, van cau, vai cac
va nam » van nam, va nay
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: doc sach ((ty nang) OR (ty hang)) xa hoi. hieu ((va nam) or (ha nam)) thuc ca dan vai cau treo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ((ty nang) OR (ty hang)) xa hoi. hieu ((va nam) OR (ha nam)) thuc ca dan vai cau treo.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach ((ty nang) OR (ty hang)) xa hoi. hieu ((va nam) or (ha nam)) thuc ca dan vai cau treo".
• Adding a wildcard symbol may retrieve word variants: doc sach ((ty nang) OR (ty hang)) xa hoi. hieu ((va nam) or (ha nam)) thuc ca dan vai cau treo*.