Perhaps you should try some spelling variations:
cong thuoc » dong thuoc, long thuoc, cong thuong
hoc nhanh » hoc nganh, hoc phan
cong thuc » cong tac
sach hoi » sach doi, sach moi, cach thoi
cuu toan » cuu hoan, cua toan, huu toan
toan hoc » toan khoa, van hoc, hoa hoc
tu sach » thu sach, su sach, te sach
hoi tap » hoi dap, hoc tap, hoi tai
mai hoi » mai khoi, dai hoi, lai hoi
va pham » van pham, va phat, va phap

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach hoi tap, nghien cuu toan hoc nhanh ((cong thuoc) or (cong thuc)) mai hoi va pham van~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach hoi tap, nghien cuu toan hoc nhanh ((cong thuoc) OR (cong thuc)) mai hoi va pham van.
• Adding a wildcard symbol may retrieve word variants: tu sach hoi tap, nghien cuu toan hoc nhanh ((cong thuoc) or (cong thuc)) mai hoi va pham van*.