Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
sach ky » sac ky, sach y, sach ty
thuc ca » thuc cua, thuc can, thuc cao
vai cau » va cau, van cau, lai chau
vai cac » va cac, tai cac, voi cac
va nam » van nam, va nay
ca dan » cac dan, ca dao
x hoi » xa hoi, o hoi, x ho

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 ky nang x hoi. hieu ((va nam) or (ha nam)) thuc ca dan ((vai cau) OR (vai cac)) treo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ky nang x hoi. hieu ((va nam) OR (ha nam)) thuc ca dan ((vai cau) OR (vai cac)) treo.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach ky nang x hoi. hieu ((va nam) or (ha nam)) thuc ca dan ((vai cau) OR (vai cac)) treo".
• Adding a wildcard symbol may retrieve word variants: doc sach ky nang x hoi. hieu ((va nam) or (ha nam)) thuc ca dan ((vai cau) OR (vai cac)) treo*.