Perhaps you should try some spelling variations:
"su sach trinh do khi đong luc" » "su sach tranh do khi đong luc", "su hanh trinh do khi đong luc", "su sach kinh do khi đong luc", "su sach trinh ky khi đong luc", "vu sach trinh do khi đong luc", "su sach trinh doi khi đong luc", "su sach trinh do thi đong luc", "su sach trinh bo khi đong luc"
"so sach nganh co khi đong luc" » "so sach ngan co khi đong luc", "so sach tranh co khi đong luc", "so cac nganh co khi đong luc", "so sach nganh cong khi đong luc", "so sach nganh hoa khi đong luc", "so sach nganh y khi đong luc", "so sanh nganh co khi đong luc", "bo sach nganh co khi đong luc", "co sach nganh 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 sach trinh do khi đong luc") or ("so sach nganh co khi đong luc"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("su sach trinh do khi đong luc") OR ("so sach nganh co khi đong luc")).
• Removing quotes may allow a broader search: (( su sach trinh do khi đong luc ) or ( so sach nganh co khi đong luc )).
• Adding a wildcard symbol may retrieve word variants: (("su sach trinh do khi đong luc") or ("so sach nganh co khi đong luc"))*.