Perhaps you should try some spelling variations:
"so sach trinh cong thai đong luc" » "so sach trinh dung thai đong luc", "so sach tranh cong thai đong luc", "so hanh trinh cong thai đong luc", "so sach kinh cong thai đong luc", "so sach trinh cong hai đong luc", "so sach trinh hong thai đong luc", "so sach trinh cong thanh đong luc", "so sanh trinh cong thai đong luc", "bo sach trinh cong thai đong luc", "co sach trinh cong thai đong luc"
"su canh tranh co khi đong luc" » "su canh trinh co khi đong luc", "su canh tranh o khi đong luc", "su canh tranh cuoc khi đong luc", "suc canh tranh co khi đong luc", "su can tranh co khi đong luc", "su anh tranh co khi đong luc"

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: (("su canh tranh co khi đong luc") or ("so sach trinh cong thai đong luc"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("su canh tranh co khi đong luc") OR ("so sach trinh cong thai đong luc")).
• Removing quotes may allow a broader search: (( su canh tranh co khi đong luc ) or ( so sach trinh cong thai đong luc )).
• Adding a wildcard symbol may retrieve word variants: (("su canh tranh co khi đong luc") or ("so sach trinh cong thai đong luc"))*.