Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, hieu ve
van hanh » van thanh, ban hanh, van anh
cau tren » cu tren, dau tren, ca tren
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
va hanh » va thanh, va danh, ban hanh
nam tu » nam thu, nam thuc
vi cau » va cau, ve cau, di cau
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) or (lieu va)) nam tu ((va hanh) OR (van hanh)) vi cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang x hoi. ((hieu van) OR (lieu va)) nam tu ((va hanh) OR (van hanh)) vi cau tren*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang x hoi. ((hieu van) or (lieu va)) nam tu ((va hanh) OR (van hanh)) vi cau tren*".