Perhaps you should try some spelling variations:
nam thuc » nam thuoc, nam thu, nam tu
manh vai » manh hai, manh va, manh khai
dan manh » dang manh, doan manh, van manh
sach ty » sach y, sach tu, sach thu
ca viet » va viet, hoa viet, san viet
tu sach » thu sach, su sach, te sach
ty nang » ky nang, ty xang, ty hang
hieu ve » hieu va, hieu van
co viet » so viet, o viet, hoc viet
nang o » nang co, nang ho, nang ro
o hoi » co hoi, o hoc, o hai

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 ty nang o hoi. hieu ve ((nam thuc) OR (am thuc)) dan manh vai ((ca viet) or (co viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty nang o hoi. hieu ve ((nam thuc) OR (am thuc)) dan manh vai ((ca viet) OR (co viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty nang o hoi. hieu ve ((nam thuc) OR (am thuc)) dan manh vai ((ca viet) or (co viet))".
• Adding a wildcard symbol may retrieve word variants: tu sach ty nang o hoi. hieu ve ((nam thuc) OR (am thuc)) dan manh vai ((ca viet) or (co viet))*.