Perhaps you should try some spelling variations:
"tu sach trinh cong khi đong luc" » "tu sach trinh dung khi đong luc", "tu sach tranh cong khi đong luc", "tu hanh trinh cong khi đong luc", "tu sach kinh cong khi đong luc", "tu sach trinh cong thai đong luc", "tu sach trinh khong khi đong luc", "tu sach trinh cong ha đong luc", "thu sach trinh cong khi đong luc", "su sach trinh cong khi đong luc", "te sach trinh cong khi 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 ("tu sach trinh cong khi đong luc"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("su canh tranh co khi đong luc") OR ("tu sach trinh cong khi đong luc")).
• Removing quotes may allow a broader search: (( su canh tranh co khi đong luc ) or ( tu sach trinh cong khi đong luc )).
• Adding a wildcard symbol may retrieve word variants: (("su canh tranh co khi đong luc") or ("tu sach trinh cong khi đong luc"))*.