Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
tru nang » tra nang, tri nang, truc nano
cac duc » cac du, cao duc, cac dac
hieu ve » hieu va, hieu van
tu nang » tu nong, tu nano, tu lang
ve cac » va cac, vien cac
va anh » van anh, va danh, va hanh
va cua » va chua, via cua, ma cua
ca cua » co cua

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