Perhaps you should try some spelling variations:
dao nguoi » cho nguoi
tay nguoi » toc nguoi
cach duoc » sach duoc, cach dung, cach hoc
mach hoc » cach hoc, dich hoc, anh hoc
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
li nguoi » loi nguoi, le nguoi, ly nguoi
tu mach » tu cach, tu manh, tu hach

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (( tu mach hoc ((tay nguoi) or (dao nguoi)) ) or ( tu ((cach duoc) OR (cac nuoc)) li nguoi ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu mach hoc ((tay nguoi) OR (dao nguoi)) ) OR ( tu ((cach duoc) OR (cac nuoc)) li nguoi )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tu mach hoc ((tay nguoi) or (dao nguoi)) ) or ( tu ((cach duoc) OR (cac nuoc)) li nguoi ))".
• Adding a wildcard symbol may retrieve word variants: (( tu mach hoc ((tay nguoi) or (dao nguoi)) ) or ( tu ((cach duoc) OR (cac nuoc)) li nguoi ))*.