Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van anh
hanh va » hang va, hanh vi
chu duc » thu duc, chua duoc, cuu duoc
cau duc » cao duc, cau luc, cau truc
sach ky » sac ky, sach y, sach kem
sach ty » sach y, sach tu, sach thu
cua tre » cua te, cuu tre, cua triet
va cua » va chua, via cua, ca cua
x hoi » xa hoi, o hoi, x ho

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