Perhaps you should try some spelling variations:
toan giao » ton giao, toan cao, hoa giao
tu thanh » thu thanh, su thanh, vu thanh
hoc giao » hoc cao
ta thanh » tai thanh, va thanh, ha thanh
tu mach » tu cach, tu manh, tu hach
tich so » tich bao, tinh son
tinh so » tinh son, tinh soc, dinh so

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