Perhaps you should try some spelling variations:
nhung cong » dung cong, thong cong, hang cong
hanh trinh » hanh chinh
viet tach » viet sach, viet tech, viet thanh
cua nhung » va nhung
cong van » cong vang, cong san, song van
tai tap » tai tao, hai tap, lai tap
o viet » so viet, hoc viet

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

• Performing a fuzzy search may retrieve terms with similar spellings: o viet tach - ((hanh trinh) or (canh tranh)) cua nhung cong van ((tai tap) OR (bai tap))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: o viet tach - ((hanh trinh) OR (canh tranh)) cua nhung cong van ((tai tap) OR (bai tap))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "o viet tach - ((hanh trinh) or (canh tranh)) cua nhung cong van ((tai tap) OR (bai tap))*".