Perhaps you should try some spelling variations:
thien van » thi van
hanh thai » nhanh thai, hinh thai, hanh tai
toan hanh » toan thanh, toan anh, tran hanh
thai cua » than cua, tai cuc, tri cua
duc toan » duc tan, duc ton, duc hoan
hieu van » hieu va, lieu va, hieu ve
cau duc » cao duc, cau luc, chu duc
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach ty, sach kem
nang o » nang co, nang ho, nang ro
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 van) OR (thien van)) cau duc toan hanh 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 van) OR (thien van)) cau duc toan hanh 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 van) OR (thien van)) cau duc toan hanh thai cua tre*".