Perhaps you should try some spelling variations:
tranh cong » thanh cong, trinh cong, tran cong
sach ngan » sach ngon, sach nha, sach han
cong thai » cong hai, hong thai, cong thanh
su sach » so sach, vu sach
ngan ky » nganh ky, nhan ky, ngan hay
su canh » suc canh, su can, su anh
ky khi » ky thi, ly khi

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( su sach ngan ky khi đong luc ) or ( su canh tranh cong thai đong luc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( su sach ngan ky khi đong luc ) OR ( su canh tranh cong thai đong luc )).
• Adding a wildcard symbol may retrieve word variants: (( su sach ngan ky khi đong luc ) or ( su canh tranh cong thai đong luc ))*.