Perhaps you should try some spelling variations:
doanh va » doan va, doanh tai, doanh cua
thu sach » thuat sach, thuoc sach, thu hoach
danh vai » danh sai, danh va, doanh van
tu sach » su sach, te sach, tu cach
cac duc » cac du, cao duc, cac dac
hieu va » lieu va, hieu qua
dang xa » dang xay, lang xa, dang ha
ky dang » ky nang, ky danh
cua tre » cua te, cuu tre, cua triet

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 (thu sach)) ky dang xa hoi. hieu va cac duc va ((danh vai) or (doanh va)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) ky dang xa hoi. hieu va cac duc va ((danh vai) OR (doanh va)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (thu sach)) ky dang xa hoi. hieu va cac duc va ((danh vai) or (doanh va)) cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) OR (thu sach)) ky dang xa hoi. hieu va cac duc va ((danh vai) or (doanh va)) cua tre*.