Perhaps you should try some spelling variations:
thien van » thi van
hieu van » hieu va, lieu va, hieu ve
cham tuc » nham thuc, pham thuc, tham thuc
van hanh » van thanh, ban hanh, van anh
co sach » bo sach, cuon sach, hoc sach
sach ky » sac ky, sach y, sach ty
va hanh » va thanh, va danh, ban hanh
cu tren » tu tren, dua tren
x hoi » xa hoi, o hoi, x ho
va cu » va cau, va chu, va su

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

• Performing a fuzzy search may retrieve terms with similar spellings: co sach ky nang x hoi. ((hieu van) or (thien van)) cham tuc ((va hanh) OR (van hanh)) va cu tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: co sach ky nang x hoi. ((hieu van) OR (thien van)) cham tuc ((va hanh) OR (van hanh)) va cu tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "co sach ky nang x hoi. ((hieu van) or (thien van)) cham tuc ((va hanh) OR (van hanh)) va cu tren".
• Adding a wildcard symbol may retrieve word variants: co sach ky nang x hoi. ((hieu van) or (thien van)) cham tuc ((va hanh) OR (van hanh)) va cu tren*.