Perhaps you should try some spelling variations:
dung ngon » dung nguon, dung ngan, dung ngo
hieu van » hieu va, thien van, lieu va
duc ngon » duc ngoc, duoi ngon, duc ton
su sach » so sach, vu sach
ty hang » ly hang, thi hang, thu hang
van lam » van nam
vi cua » vai cua, di cua
cua tu » cua tuc, cua su, cua cu

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 hang) or (ty xang)) xa hoi. hieu van lam ((duc ngon) OR (dung ngon)) hanh vi cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((ty hang) OR (ty xang)) xa hoi. hieu van lam ((duc ngon) OR (dung ngon)) hanh vi cua tu.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((ty hang) or (ty xang)) xa hoi. hieu van lam ((duc ngon) OR (dung ngon)) hanh vi cua tu".
• Adding a wildcard symbol may retrieve word variants: su sach ((ty hang) or (ty xang)) xa hoi. hieu van lam ((duc ngon) OR (dung ngon)) hanh vi cua tu*.