Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
thu sach » tu sach, thuat sach, thuoc sach
hieu van » hieu va, thien van, lieu va
dua tren » dung tren
hieu ve » hieu va
sach ty » sach y, sach tu, sach thu
nang xa » nang x, lang xa, nang ma
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh
ty nang » ky nang, ty xang, ty hang
cuu tre » cua tre, cau tren, cau treo

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

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