Perhaps you should try some spelling variations:
mach tinh » mach tich, manh tinh, trach tinh
mach dinh » hoach dinh, xac dinh, mach dien
ton giao » toan giao, so giao, don gian
hoc giao » hoc cao
tinh hoc » sinh hoc, tin hoc, hinh hoc
tu mach » tu cach, tu manh, tu hach
giai » gia, gian, gioi

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