Perhaps you should try some spelling variations:
doan manh » doan minh, hoang manh, tran manh
hieu van » hieu va, thien van, lieu va
dan manh » dang manh, van manh, day manh
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
co viet » so viet, o viet, hoc viet
x hoi » xa hoi, o hoi, x ho

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 ky nang x hoi. hieu van nam thu ((dan manh) or (doan manh)) mai co viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang x hoi. hieu van nam thu ((dan manh) OR (doan manh)) mai co viet.
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang x hoi. hieu van nam thu ((dan manh) or (doan manh)) mai co viet*.