Perhaps you should try some spelling variations:
viet hanh » viet thanh, viet anh, viet han
hieu vien » hieu hien, thieu nien, hieu tieng
hieu viec » nhieu viec, hieu ve, sieu viet
hoc viet » hoc hien
su triet » su viet, su tien, ve triet
su sach » so sach, vu sach
cac hoc » cach hoc, cac hop, bac hoc
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
su hien » su kien, su tien, thu hien

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 ky nang xa hoi. ((hieu vien) or (hieu viec)) cac hoc viet hanh vi ((su triet) or (su hien))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang xa hoi. ((hieu vien) OR (hieu viec)) cac hoc viet hanh vi ((su triet) OR (su hien)).
• Adding a wildcard symbol may retrieve word variants: su sach ky nang xa hoi. ((hieu vien) or (hieu viec)) cac hoc viet hanh vi ((su triet) or (su hien))*.