Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hieu van » hieu va, thien van, lieu va
cua tre » cua te, cua triet, dua tren
minh ve » dinh ve, minh va, kinh ve
sach ty » sach y, sach tu, sach thu
van hoc » van hoa
cuu tre » cau tren, cau treo
ty nang » ky nang, ty xang, ty hang
hoc du » hoc duc, hoc dau, hoc dua
du van » duy van, duc van, tu van
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 ty nang ((x hoi) or (o hoi)). hieu van hoc du van minh ve ((cua tre) OR (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ty nang ((x hoi) OR (o hoi)). hieu van hoc du van minh ve ((cua tre) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ty nang ((x hoi) or (o hoi)). hieu van hoc du van minh ve ((cua tre) OR (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: thu sach ty nang ((x hoi) or (o hoi)). hieu van hoc du van minh ve ((cua tre) OR (cuu tre))*.