Perhaps you should try some spelling variations:
hanh tai » thanh tai, hang tai, han tai
tai cua » thai cua, tai cuc, tri cua
va hanh » van hanh, va thanh, va danh
cac luc » cau luc, coc luc, cac nuoc
hieu ve » hieu va, hieu van
dai hai » dai han, dai hoi, dai tai
sach ky » sac ky, sach y, sach kem
sach ty » sach y, sach tu, sach thu
cua tre » cua te, cuu tre, cua triet
ve cac » va cac, vien cac
luc va » duc va, tuc va, loc va

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 ky) OR (sach ty)) nang ((cau hoi) or (dai hai)). hieu ve cac luc va hanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ky) OR (sach ty)) nang ((cau hoi) OR (dai hai)). hieu ve cac luc va hanh tai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ky) OR (sach ty)) nang ((cau hoi) or (dai hai)). hieu ve cac luc va hanh tai cua tre".
• Adding a wildcard symbol may retrieve word variants: su ((sach ky) OR (sach ty)) nang ((cau hoi) or (dai hai)). hieu ve cac luc va hanh tai cua tre*.