Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
vat hanh » vat thanh, van hanh, va hanh
nam thuc » nam thuoc, am thuc, nam thu
cam thuc » am thuc, cam thu, can thuc
hanh di » hanh vi, hanh de, hang di
su sach » so sach, vu sach
cuu tre » cua tre, cau tren, cau treo
hieu ve » hieu va
sach v » sach va, sach y, sach 2
v nang » va nang, vu nang, van 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 x hoi. ((hieu ve) or (hieu van)) ((cam thuc) OR (nam thuc)) vat hanh di cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach v nang x hoi. ((hieu ve) OR (hieu van)) ((cam thuc) OR (nam thuc)) vat hanh di cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach v nang x hoi. ((hieu ve) or (hieu van)) ((cam thuc) OR (nam thuc)) vat hanh di cuu tre".
• Adding a wildcard symbol may retrieve word variants: su sach v nang x hoi. ((hieu ve) or (hieu van)) ((cam thuc) OR (nam thuc)) vat hanh di cuu tre*.