Perhaps you should try some spelling variations:
nhanh thai » nhanh thi, nhanh thanh, nhanh thang
hanh thai » hinh thai, hanh tai, anh thai
cac duc » cac du, cao duc, cac dac
duc ban » duc tan, duc van, dua ban
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach ty, sach kem
hieu ve » hieu va, hieu van
nang o » nang co, nang ho, nang ro
ve cac » va cac, vien cac
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 ky) OR (sach y)) nang o hai. hieu ve cac duc ban ((hanh thai) or (nhanh thai)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sach y)) nang o hai. hieu ve cac duc ban ((hanh thai) OR (nhanh thai)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) OR (sach y)) nang o hai. hieu ve cac duc ban ((hanh thai) or (nhanh thai)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) OR (sach y)) nang o hai. hieu ve cac duc ban ((hanh thai) or (nhanh thai)) cua tre*.