Perhaps you should try some spelling variations:
hinh thai » sinh thai, tinh thai, dinh thi
hanh thai » nhanh thai, hanh tai, anh thai
cac duc » cac du, cao duc, cac dac
duc van » duc va, duc tan, duc manh
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 hoi » co hoi, o hoc, o hai

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

• Performing a fuzzy search may retrieve terms with similar spellings: te ((sach ky) or (sach y)) nang o hoi. hieu ve cac duc van ((hanh thai) OR (hinh thai)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te ((sach ky) OR (sach y)) nang o hoi. hieu ve cac duc van ((hanh thai) OR (hinh thai)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te ((sach ky) or (sach y)) nang o hoi. hieu ve cac duc van ((hanh thai) OR (hinh thai)) cua tre".
• Adding a wildcard symbol may retrieve word variants: te ((sach ky) or (sach y)) nang o hoi. hieu ve cac duc van ((hanh thai) OR (hinh thai)) cua tre*.