Perhaps you should try some spelling variations:
doan manh » doan minh, hoang manh, tran manh
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
day manh » van manh, ha manh
duc manh » suc manh, duc anh, duc minh
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
co viet » so viet, o viet, hoc viet
tai co » mai co, tai so, tri co
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 thuc ((((day manh) OR (duc manh))) or (doan manh)) tai co viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang x hoi. hieu van nam thuc ((((day manh) OR (duc manh))) OR (doan manh)) tai co viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang x hoi. hieu van nam thuc ((((day manh) OR (duc manh))) or (doan manh)) tai co viet".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang x hoi. hieu van nam thuc ((((day manh) OR (duc manh))) or (doan manh)) tai co viet*.