Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
van hanh » van thanh, ban hanh, van anh
sach thu » sach thue, sach thieu, sach tham
can thuc » dan thuc, van thuc, cay thuc
day thuc » dan thuc, cay thuc, dai thuc
sach ty » sach y, sach tu, xach tay
nang xa » nang x, lang xa, nang ma
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: su ((sach ty) OR (sach thu)) nang xa hoi. hieu vien ((day thuc) or (can thuc)) van hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ty) OR (sach thu)) nang xa hoi. hieu vien ((day thuc) OR (can thuc)) van hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ty) OR (sach thu)) nang xa hoi. hieu vien ((day thuc) or (can thuc)) van hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: su ((sach ty) OR (sach thu)) nang xa hoi. hieu vien ((day thuc) or (can thuc)) van hanh vi cua tre*.