Perhaps you should try some spelling variations:
"tu sach trinh do khi đong luc" » "tu sach tranh do khi đong luc", "tu hanh trinh do khi đong luc", "tu sach kinh do khi đong luc", "su sach trinh do khi đong luc", "te sach trinh do khi đong luc", "tu cach trinh do khi đong luc", "tu sach trinh doi khi đong luc", "tu sach trinh do thi đong luc", "tu sach trinh co khi đong luc"
"thu sach trinh ky khi đong luc" » "thu sach tranh ky khi đong luc", "thu hanh trinh ky khi đong luc", "thu sach kinh ky khi đong luc", "thuat sach trinh ky khi đong luc", "thuoc sach trinh ky khi đong luc", "thu hoach trinh ky khi đong luc", "thu sach trinh ky thi đong luc", "thu sach trinh ly khi đong luc"

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 trinh do khi đong luc") or ("thu sach trinh ky khi đong luc"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("tu sach trinh do khi đong luc") OR ("thu sach trinh ky khi đong luc")).
• Removing quotes may allow a broader search: (( tu sach trinh do khi đong luc ) or ( thu sach trinh ky khi đong luc )).
• Adding a wildcard symbol may retrieve word variants: (("tu sach trinh do khi đong luc") or ("thu sach trinh ky khi đong luc"))*.