Perhaps you should try some spelling variations:
"tu cach hoc may nguoi" » "tu cach hoc tay nguoi", "tu cach hoc ma nguoi", "tu cach hoc mac nguoi", "tu cach thuc may nguoi", "tu cach thoi may nguoi", "tu dich hoc may nguoi", "tu cac hoc may nguoi"
"su mach hoc may nguoi" » "su mach hoc tay nguoi", "su mach hoc ma nguoi", "su mach hoc mac nguoi", "su dich hoc may nguoi", "su anh hoc may nguoi", "su bac hoc may nguoi", "su sach hoc may nguoi"
"su mach hoc lay nguoi" » "su mach hoc tay nguoi", "su mach hoc lam nguoi", "su mach hoc ly nguoi", "su dich hoc lay nguoi", "su anh hoc lay nguoi", "su bac hoc lay nguoi", "su sach hoc lay nguoi", "su mach hoc lap 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: (("tu cach hoc may nguoi") or ((("su mach hoc may nguoi") OR ("su mach hoc lay nguoi"))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("tu cach hoc may nguoi") OR ((("su mach hoc may nguoi") OR ("su mach hoc lay nguoi")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"tu cach hoc may nguoi\") or (((\"su mach hoc may nguoi\") OR (\"su mach hoc lay nguoi\"))))".
• Removing quotes may allow a broader search: (( tu cach hoc may nguoi ) or ((( su mach hoc may nguoi ) OR ( su mach hoc lay nguoi )))).
• Adding a wildcard symbol may retrieve word variants: (("tu cach hoc may nguoi") or ((("su mach hoc may nguoi") OR ("su mach hoc lay nguoi"))))*.