Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
sach ky » sac ky, sach y, sach ty
cuu tre » cau tren, cau treo
danh vi » hanh vi, dinh vi, danh di
va danh » va dinh, va dan, va hanh
hac tuc » thac toc, thai tuc
cua tre » cua te, cua triet, dua tren
hieu va » lieu va, hieu qua
tuc va » thuc va, truc va, tuc xa
va hac » van hac, va khac, va cac
o hoi » co hoi, o hoc, o hai
x hoi » xa hoi, x ho, 5 hoi

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ky nang ((x hoi) or (o hoi)). hieu va hac tuc va danh vi ((cuu tre) OR (cua tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky nang ((x hoi) OR (o hoi)). hieu va hac tuc va danh vi ((cuu tre) OR (cua tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ky nang ((x hoi) or (o hoi)). hieu va hac tuc va danh vi ((cuu tre) OR (cua tre))".
• Adding a wildcard symbol may retrieve word variants: thu sach ky nang ((x hoi) or (o hoi)). hieu va hac tuc va danh vi ((cuu tre) OR (cua tre))*.