Perhaps you should try some spelling variations:
khanh thi » nhanh thi, khanh thu, nhanh thai
van khanh » van thanh, van hanh, van anh
tu sach » thu sach, su sach, te sach
thi cua » thai cua, thi cuc, tri cua
duc van » duc va, duc tan, duc manh
cac duc » cac du, cao duc, cac dac
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, may nang
ve cac » va cac, vien cac
v nang » va nang, vu nang, van nang
o hoi » co hoi, o hoc, o hoa
o hai » co hai, so hai, o lai

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ((y nang) or (v nang)) ((o hoi) or (o hai)). hieu ve cac duc van khanh thi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((y nang) OR (v nang)) ((o hoi) OR (o hai)). hieu ve cac duc van khanh thi cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ((y nang) or (v nang)) ((o hoi) or (o hai)). hieu ve cac duc van khanh thi cua tre*.