Perhaps you should try some spelling variations:
hieu van » hieu va, thien van
cam thuc » am thuc, nam thuc, cam thu
vat hanh » vat thanh, van hanh, va hanh
su sach » so sach, vu sach
nang xa » nang x, lang xa, nang ma
hieu ve » hieu va
hanh di » hanh vi, hanh de, hang di
cuu tre » cua tre, cau tren, cau treo
y nang » ky nang, ly nang, v nang
di cuu » di cau, di cua, dinh cuu

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