Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
cua viet » ca viet, hoa viet, cua vat
tu sach » thu sach, su sach, te sach
ky lang » ky dang, ky tang, tay lang
van cam » van nam, van lam, van cau
cam luc » cam xuc, cau luc
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
luc va » duc va, tuc va, loc va

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 lang) or (ky nang)) xa hoi. hieu van cam luc va hanh vi ((cua tre) or (cua viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky lang) OR (ky nang)) xa hoi. hieu van cam luc va hanh vi ((cua tre) OR (cua viet)).
• Adding a wildcard symbol may retrieve word variants: tu sach ((ky lang) or (ky nang)) xa hoi. hieu van cam luc va hanh vi ((cua tre) or (cua viet))*.