Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
tang ma » mang may, tang van
cua tre » cua te, cuu tre, cua triet
o viet » so viet, hoc viet
dam tu » nam tu, tam tu, dam thuc
y tang » ky tang, 6 tang, 7 tang
cam tu » cam thu, nam tu, tam tu
ma hoi » mai hoi, xa hoi, ma hoa

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 y tang ma hoi. hieu van ((cam tu) or (dam tu)) van hanh vi ((cua tre) or (o viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y tang ma hoi. hieu van ((cam tu) OR (dam tu)) van hanh vi ((cua tre) OR (o viet)).
• Adding a wildcard symbol may retrieve word variants: tu sach y tang ma hoi. hieu van ((cam tu) or (dam tu)) van hanh vi ((cua tre) or (o viet))*.