Perhaps you should try some spelling variations:
"so canh tranh cua cach van le trung" » "so canh doanh cua cach van le trung", "so canh manh cua cach van le trung", "so canh tranh cua cac van le trung", "so canh tranh ca cach van le trung", "so canh tranh cua bach van le trung", "so canh tranh cua canh van le trung", "so canh tranh cua cach van do trung", "so sanh tranh cua cach van le trung", "bo canh tranh cua cach van le trung", "so danh tranh cua cach van le trung", "so canh tranh cua cach van de trung", "so canh tranh cua cach ban le trung"
"co sach tri tue bach va he thong" » "co sach tai tue bach va he thong", "co sach tren tue bach va he thong", "co sach bai tue bach va he thong", "co sach tri truc bach va he thong", "co sach tri thi bach va he thong", "co sach tri vu bach va he thong", "bo sach tri tue bach va he thong", "cuon sach tri tue bach va he thong", "hoc sach tri tue bach va he thong", "co sach tri tue bach van he thong", "co sach tri tue bach ha he thong", "co sach tri tue sach va he thong", "co sach tri tue bach va che thong", "co sach tri tue bach va ghe thong", "co sach tri tue bach va de thong"

Try widening your search to All Fields.

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("co sach tri tue bach va he thong") or ("so canh tranh cua cach van le trung"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("co sach tri tue bach va he thong") OR ("so canh tranh cua cach van le trung")).
• Removing quotes may allow a broader search: (( co sach tri tue bach va he thong ) or ( so canh tranh cua cach van le trung )).
• Adding a wildcard symbol may retrieve word variants: (("co sach tri tue bach va he thong") or ("so canh tranh cua cach van le trung"))*.