Perhaps you should try some spelling variations:
nang mai » nang ma, nang tai, lang mai
hieu van » hieu va, thien van, lieu va
cua viet » ca viet, hoa viet, cua vat
tu sach » thu sach, su sach, te sach
mai hoi » mai khoi, dai hoi, lai hoi
van cau » van dau, van hau, van chat
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
cau tu » dau tu, cau truc

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