Perhaps you should try some spelling variations:
mach dinh » hoach dinh, xac dinh, mach dien
manh tinh » man tinh, manh binh, canh tinh
tinh son » tinh toan, dinh so, tinh hoc
dinh van » sinh vat
hoc giao » hoc cao
tu manh » tu minh, tu hanh, vu manh
so giao » so giai
tu mach » tu cach, 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 manh tinh son - so giao ) or ( tu mach dinh van - hoc giao ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu manh tinh son - so giao ) OR ( tu mach dinh van - hoc giao )).
• Adding a wildcard symbol may retrieve word variants: (( tu manh tinh son - so giao ) or ( tu mach dinh van - hoc giao ))*.