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
nang xa » nang x, lang xa, mang xa
nang ma » tang ma, sang ma, nang cao
van cau » van dau, van hau, van chat
va hanh » van hanh, va thanh, va danh
cuu tre » cua tre, cau tren, cau treo
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 xa) OR (nang ma)) hoi. hieu van cau tu va hanh vi ((cuu tre) or (cua viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y ((nang xa) OR (nang ma)) hoi. hieu van cau tu va hanh vi ((cuu tre) OR (cua viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y ((nang xa) OR (nang ma)) hoi. hieu van cau tu va hanh vi ((cuu tre) or (cua viet))".
• Adding a wildcard symbol may retrieve word variants: tu sach y ((nang xa) OR (nang ma)) hoi. hieu van cau tu va hanh vi ((cuu tre) or (cua viet))*.