Perhaps you should try some spelling variations:
cach dinh » cac dinh, cach kinh, hoach dinh
toan giao » toan cao, hoa giao
mach tinh » mach tich, manh tinh, trach tinh
ton giao » so giao, don gian, hoa giao
tinh hoc » sinh hoc, tin hoc, hinh hoc
hoc giao » hoc cao
tu cach » tu cac
tu mach » tu manh, tu hach, tu sach

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 dinh so - ((ton giao) OR (toan giao)) ) or ( tu mach tinh hoc - hoc giao ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu cach dinh so - ((ton giao) OR (toan giao)) ) OR ( tu mach tinh hoc - hoc giao )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tu cach dinh so - ((ton giao) OR (toan giao)) ) or ( tu mach tinh hoc - hoc giao ))".
• Adding a wildcard symbol may retrieve word variants: (( tu cach dinh so - ((ton giao) OR (toan giao)) ) or ( tu mach tinh hoc - hoc giao ))*.