Perhaps you should try some spelling variations:
sach hoi » sach doi, sach moi, cach thoi
cuu cong » cua cong, thu cong, cac cong
cong coc » cong cuoc, cong cac, cong co
coc toan » ngoc toan, coc khoan, quoc toan
co sach » bo sach, cuon sach, hoc sach
hoi tap » hoi dap, hoc tap, hoi tai
va phan » van phan, 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: co sach hoi tap, nghien cuu cong coc toan khoa ((hoc xa) OR (hoc ma)) hoi va phan tu~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "co sach hoi tap, nghien cuu cong coc toan khoa ((hoc xa) OR (hoc ma)) hoi va phan tu".
• Adding a wildcard symbol may retrieve word variants: co sach hoi tap, nghien cuu cong coc toan khoa ((hoc xa) OR (hoc ma)) hoi va phan tu*.