Perhaps you should try some spelling variations:
sach tranh » canh tranh
tranh cong » thanh cong, trinh cong, tran cong
trinh han » trinh quan
thu sach » thuat sach, thuoc sach, thu hoach
cong khi » cong thai, khong khi, co khi
tu sach » te sach, tu cach, vu sach
han khi » ban khi, van khi, than khai
su sach » so sach, vu sach

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (( ((tu sach) OR (thu sach)) trinh han khi đong luc ) OR ( su sach tranh cong khi đong luc ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( ((tu sach) OR (thu sach)) trinh han khi đong luc ) or ( su sach tranh cong khi đong luc ))~".
• Adding a wildcard symbol may retrieve word variants: (( ((tu sach) OR (thu sach)) trinh han khi đong luc ) or ( su sach tranh cong khi đong luc ))*.