Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
vat hanh » vat thanh, van hanh, va hanh
van nang » van quang, van ban, van dong
cam thuc » am thuc, nam thuc, cam thu
su sach » so sach, vu sach
hanh di » hanh vi, hanh de, hang di
cuu tre » cua tre, cau tren, cau treo
hieu ve » hieu va
v nang » va nang, vu nang, voi nang
di cuu » di cau, di cua, dinh cuu
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: su sach ((v nang) OR (van nang)) x hoi. ((hieu ve) or (hieu van)) cam thuc vat hanh di cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((v nang) OR (van nang)) x hoi. ((hieu ve) OR (hieu van)) cam thuc vat hanh di cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((v nang) OR (van nang)) x hoi. ((hieu ve) or (hieu van)) cam thuc vat hanh di cuu tre".
• Adding a wildcard symbol may retrieve word variants: su sach ((v nang) OR (van nang)) x hoi. ((hieu ve) or (hieu van)) cam thuc vat hanh di cuu tre*.