Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
tru nang » tra nang, tri nang, truc nano
hanh dai » hanh tai, hanh dao, vanh dai
va triet » va thiet, va trien, ve triet
va hanh » van hanh, va thanh, va danh
tu lang » cu lang, tu lanh, xu lang
dai va » mai va
va cao » va cac, va dao, va bao
va co » vo co

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 ((tu lang) or (tru nang)) xa hoi. hieu ((va cao) OR (va co)) duc va hanh dai va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((tu lang) OR (tru nang)) xa hoi. hieu ((va cao) OR (va co)) duc va hanh dai va triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((tu lang) or (tru nang)) xa hoi. hieu ((va cao) OR (va co)) duc va hanh dai va triet".
• Adding a wildcard symbol may retrieve word variants: toc sach ((tu lang) or (tru nang)) xa hoi. hieu ((va cao) OR (va co)) duc va hanh dai va triet*.