Perhaps you should try some spelling variations:
nghien cac » nghiep cach, nghien cuu, nghiep cay
sach hoi » sach doi, sach moi, cach thoi
cac cong » cua cong
co sach » bo sach, cuon sach, hoc sach
hoi tap » hoi dap, hoc tap, hoi tai
cong co » dong co, cong cu, cong so
co toan » co ton, so toan, cong toan
hoc hoc » hoc hoa, hoc hoi, duoc hoc
toc hoc » toan hoc, duoc hoc
hoi ban » hoi dan, hoi bai, doi ban
phap tu » phan tu, pham tu

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 cac cong co toan ((hoc hoc) or (toc hoc)) xa hoi ban phap tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: co sach hoi tap, nghien cac cong co toan ((hoc hoc) OR (toc hoc)) xa hoi ban phap tu.
• Adding a wildcard symbol may retrieve word variants: co sach hoi tap, nghien cac cong co toan ((hoc hoc) or (toc hoc)) xa hoi ban phap tu*.