Perhaps you should try some spelling variations:
sach truc » sach tren, sach thu, sach thue
cach thuc » anh thuc, cac thu
hieu van » hieu va, thien van, lieu va
cuc ban » cua ban, cac ban, cuu ban
van cam » van nam, van lam, van cau
nano xa » nano va, nano bac, nano cau
cua tre » cua te, cuu tre, cua triet
vi cua » vai cua, di cua

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 truc) OR (cach thuc)) nano xa hoi. hieu van cam ((cuc ban) or (cuu van)) hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach truc) OR (cach thuc)) nano xa hoi. hieu van cam ((cuc ban) OR (cuu van)) hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach truc) OR (cach thuc)) nano xa hoi. hieu van cam ((cuc ban) or (cuu van)) hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach truc) OR (cach thuc)) nano xa hoi. hieu van cam ((cuc ban) or (cuu van)) hanh vi cua tre*.