Perhaps you should try some spelling variations:
cham thuc » nham thuc, pham thuc, tham thuc
van nang » van quang, van dong, van dung
vat hanh » vat thanh, van hanh, va hanh
su sach » so sach, vu sach
hieu ve » hieu va, hieu van
ve cham » va cham, ve chat, vu cham
vi cua » vai cua
di cua » dai cua, doi cua, de cua

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 ((van nang) OR (van ban)) xa hoi. hieu ve cham thuc vat hanh ((vi cua) or (di cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((van nang) OR (van ban)) xa hoi. hieu ve cham thuc vat hanh ((vi cua) OR (di cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((van nang) OR (van ban)) xa hoi. hieu ve cham thuc vat hanh ((vi cua) or (di cua)) tre".
• Adding a wildcard symbol may retrieve word variants: su sach ((van nang) OR (van ban)) xa hoi. hieu ve cham thuc vat hanh ((vi cua) or (di cua)) tre*.