Perhaps you should try some spelling variations:
"sach dac cho cua thoi 16+" » "sach dao cho cua thoi 16+", "sach dat cho cua thoi 16+", "sach bac cho cua thoi 16+", "sach dac cho cua hoi 16+", "sach dac cho cua toi 16+", "sach dac cho cua khoi 16+", "sach day cho cua thoi 16+", "sach danh cho cua thoi 16+", "sach dac co cua thoi 16+", "sach dac chi cua thoi 16+", "sach dac cho ca thoi 16+"
"sach bao cho lua tuoi 16+" » "sach dao cho lua tuoi 16+", "sach bai cho lua tuoi 16+", "sach bac cho lua tuoi 16+", "sach bao cho sua tuoi 16+", "sach bao cho tuan tuoi 16+", "sach bao cho lua doi 16+", "sach bao cao lua tuoi 16+", "sach bao che lua tuoi 16+", "sach cao cho lua tuoi 16+", "sach bao cho qua tuoi 16+", "sach bao chat lua tuoi 16+", "sach bao cho lua tuoi 1+"

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: (("sach dac cho cua thoi 16+") or ("sach bao cho lua tuoi 16+"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("sach dac cho cua thoi 16+") OR ("sach bao cho lua tuoi 16+")).
• Removing quotes may allow a broader search: (( sach dac cho cua thoi 16+ ) or ( sach bao cho lua tuoi 16+ )).
• Adding a wildcard symbol may retrieve word variants: (("sach dac cho cua thoi 16+") or ("sach bao cho lua tuoi 16+"))*.