Perhaps you should try some spelling variations:
phap toan » phap hoan, phap luan, phap phan
sach hoi » sach doi, sach moi, cach thoi
hoc toan » hoc tan, hop toan, hoa toan
khoa hoc » hoa hoc
hoc giai » hoc giao, hoc dai, so giai
giai hoc » dai hoc, bai hoc, thai hoc
hoc luan » hoc quan, nuoc luan, hoc luong
so sach » so sanh, bo sach, co sach
hoi tap » hoi dap, hoc tap, hoi tai
cuu mot » cua mot, cuu mo, huu mot
van van » van ban, tan van, san van

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach hoi tap, nghien cuu mot ((hoc toan) or (phap toan)) khoa hoc giai hoc luan van van~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach hoi tap, nghien cuu mot ((hoc toan) OR (phap toan)) khoa hoc giai hoc luan van van.
• Adding a wildcard symbol may retrieve word variants: so sach hoi tap, nghien cuu mot ((hoc toan) or (phap toan)) khoa hoc giai hoc luan van van*.