Perhaps you should try some spelling variations:
cac khoi » cac thoi, cac khoan, cach thoi
van hang » van khang, van hoang, van thang
mai khoi » mai khoa, tai khoa, dai khoa
tu sach » thu sach, te sach, tu cach
duc van » duc va, duc tan, duc manh
ve pham » vi pham, v pham, ve phan
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
ky lang » ky nang, ky dang, ky tang
su sach » so sach, vu sach
va cua » va chua, via cua, ca cua

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 (su sach)) ky lang ((mai khoi) or (cac khoi)). hieu ve pham duc van hang va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (su sach)) ky lang ((mai khoi) OR (cac khoi)). hieu ve pham duc van hang va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (su sach)) ky lang ((mai khoi) or (cac khoi)). hieu ve pham duc van hang va cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) OR (su sach)) ky lang ((mai khoi) or (cac khoi)). hieu ve pham duc van hang va cua tre*.