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
duoc hoc » quoc hoi
co sach » bo sach, cuon sach, hoc sach
cong co » dong co, cong cu, cong so
co toan » co ton, so toan, cong toan
hoc hoc » hoc hoa, toc hoc, hoc hoi
va phap » va phat, ban phap
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 dap, nghien cac cong co toan ((hoc hoc) or (duoc hoc)) xa hoi va phap tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: co sach hoi dap, nghien cac cong co toan ((hoc hoc) OR (duoc hoc)) xa hoi va phap tu.
• Adding a wildcard symbol may retrieve word variants: co sach hoi dap, nghien cac cong co toan ((hoc hoc) or (duoc hoc)) xa hoi va phap tu*.