Perhaps you should try some spelling variations:
sach dau » sach dao, sach dat, sach mau
dau bang » dau quang, dang bang, cao bang
cam thuc » am thuc, nam thuc, cam thu
su sach » so sach, vu sach
bang xa » lang xa, bang va, mang xa
hieu ve » hieu va, hieu van
va hanh » van hanh, va thanh, va danh
vai va » mai va, dai va, hai va
vi va » vi van, vu va, bi va

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach dau bang xa hoi. hieu ve ((cam thuc) or (nam thu)) va hanh ((vi va) OR (vai va)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach dau bang xa hoi. hieu ve ((cam thuc) OR (nam thu)) va hanh ((vi va) OR (vai va)) triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach dau bang xa hoi. hieu ve ((cam thuc) or (nam thu)) va hanh ((vi va) OR (vai va)) triet".
• Adding a wildcard symbol may retrieve word variants: su sach dau bang xa hoi. hieu ve ((cam thuc) or (nam thu)) va hanh ((vi va) OR (vai va)) triet*.