Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
hanh tai » thanh tai, hang tai, han tai
nang co » nang cao, nang doc, nang noi
hieu va » lieu va, hieu qua
duc van » duc tan, duc manh, duc phan
tai cua » thai cua, tai cuc, tri cua
y nang » ky nang, ly nang, v nang
co hoi » co hoc, co loi
va cao » va cac, va co, va dao
cua te » cua tu

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