Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
tang ky » dang ky, trong ky, tang khu
nang xa » nang x, lang xa, nang ma
cac duc » cao duc, cac dac, cac nuoc
va hanh » van hanh, va thanh, va danh
hanh di » hanh vi, hanh de, hang di
di cua » dai cua, doi cua, de cua
cua su » qua su

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: thu ((van ky) or (tang ky)) nang xa hoi. hieu vien ((cac duc) OR (cac du)) va hanh di cua su~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((van ky) OR (tang ky)) nang xa hoi. hieu vien ((cac duc) OR (cac du)) va hanh di cua su.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((van ky) or (tang ky)) nang xa hoi. hieu vien ((cac duc) OR (cac du)) va hanh di cua su".
• Adding a wildcard symbol may retrieve word variants: thu ((van ky) or (tang ky)) nang xa hoi. hieu vien ((cac duc) OR (cac du)) va hanh di cua su*.