Perhaps you should try some spelling variations:
"tim mach hoc lam nguoi" » "tim mach hoc dao nguoi", "tim dich hoc lam nguoi", "tim anh hoc lam nguoi", "tim bac hoc lam nguoi", "tim mach duoc lam nguoi"
"tim cach hoc lam nguoi" » "tim cach hoc dao nguoi", "tinh cach hoc lam nguoi", "tu cach hoc lam nguoi", "em cach hoc lam nguoi", "tim cach thuc lam nguoi", "tim cach thoi lam nguoi", "tim dich hoc lam nguoi", "tim cach duoc lam nguoi"
"toc sach hoc tay nguoi" » "toc sach hoc toc nguoi", "toc sach hoc dao nguoi", "hoc sach hoc tay nguoi", "doc sach hoc tay nguoi", "thuoc sach hoc tay nguoi", "toc sach hoi tay nguoi", "toc sach duoc tay nguoi", "toc sach nuoc tay nguoi", "toc sach toc tay nguoi", "toc sach hoc tap nguoi", "toc sach hoc may 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: (((("tim mach hoc lam nguoi") OR ("tim cach hoc lam nguoi"))) or ("toc sach hoc tay nguoi"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("tim mach hoc lam nguoi") OR ("tim cach hoc lam nguoi"))) OR ("toc sach hoc tay nguoi")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"tim mach hoc lam nguoi\") OR (\"tim cach hoc lam nguoi\"))) or (\"toc sach hoc tay nguoi\"))".
• Removing quotes may allow a broader search: (((( tim mach hoc lam nguoi ) OR ( tim cach hoc lam nguoi ))) or ( toc sach hoc tay nguoi )).
• Adding a wildcard symbol may retrieve word variants: (((("tim mach hoc lam nguoi") OR ("tim cach hoc lam nguoi"))) or ("toc sach hoc tay nguoi"))*.