Perhaps you should try some spelling variations:
thien chien » thien nhien
manh hanh » xanh hanh, danh thanh, minh thanh
cac duc » cao duc, cac dac, cac nuoc
tu sach » thu sach, su sach, te sach
mai hoi » mai khoi, dai hoi, lai hoi
tu hanh » du hanh, lu hanh, thuc hanh
tu hang » thu hang, tu hung, ty hang
ca viet » va viet, co viet, hoa viet
vi ca » vit ca, li ca, va ca

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ((tu hang) or (tu hanh)) mai hoi. thien chien ((cac duc) OR (cac du)) manh hanh vi ca viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((tu hang) OR (tu hanh)) mai hoi. thien chien ((cac duc) OR (cac du)) manh hanh vi ca viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((tu hang) or (tu hanh)) mai hoi. thien chien ((cac duc) OR (cac du)) manh hanh vi ca viet".
• Adding a wildcard symbol may retrieve word variants: tu sach ((tu hang) or (tu hanh)) mai hoi. thien chien ((cac duc) OR (cac du)) manh hanh vi ca viet*.