Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
van hang » van khang, van hoang, van thang
tu sach » thu sach, su sach, te sach
qua cac » cua cac
cac duc » cac du, cao duc, cac dac
duc van » duc va, duc tan, duc manh
vai cua » dai cua, hai cua, lai cua
vi cua » di cua
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: ((tu sach) or (toc sach)) ky nang x hoi. hieu qua cac duc van hang ((vi cua) OR (vai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (toc sach)) ky nang x hoi. hieu qua cac duc van hang ((vi cua) OR (vai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (toc sach)) ky nang x hoi. hieu qua cac duc van hang ((vi cua) OR (vai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (toc sach)) ky nang x hoi. hieu qua cac duc van hang ((vi cua) OR (vai cua)) tre*.