Perhaps you should try some spelling variations:
"su sach hoc may nguoi" » "su sach hoc ma nguoi", "su sach hoc lay nguoi", "su sach hoc mac nguoi", "su cach hoc may nguoi", "su sach hoi may nguoi", "su sach duoc may nguoi", "vu sach hoc may nguoi"
"su mach hoc tay nguoi" » "su mach hoc toc nguoi", "su mach hoc dao nguoi", "su cach hoc tay nguoi", "su dich hoc tay nguoi", "su anh hoc tay nguoi", "su mach toc tay nguoi", "su mach hoc tap nguoi", "su mach hoc tai nguoi"
"so sach hoc lam nguoi" » "so sach hoc dao nguoi", "so cach hoc lam nguoi", "so sach hoi lam nguoi", "so sach duoc lam nguoi", "so sanh hoc lam nguoi", "bo sach hoc lam nguoi", "co sach hoc lam nguoi"

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 hoc may nguoi") or ("su mach hoc tay nguoi"))) or ("so sach hoc lam nguoi"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("su sach hoc may nguoi") OR ("su mach hoc tay nguoi"))) OR ("so sach hoc lam nguoi")).
• Removing quotes may allow a broader search: (((( su sach hoc may nguoi ) or ( su mach hoc tay nguoi ))) or ( so sach hoc lam nguoi )).
• Adding a wildcard symbol may retrieve word variants: (((("su sach hoc may nguoi") or ("su mach hoc tay nguoi"))) or ("so sach hoc lam nguoi"))*.