Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
sach thue » sach thu, sach thieu, sach tham
va hanh » van hanh, va thanh, va danh
sach ty » sach y, sach tu, sach thu
vien da » vien dai, hien dai
tac va » tac da, tac xa, tuc va
da tac » va tac, da tai, da tao
vi cua » vai cua, di cua
ma hoi » mai hoi, ma hoa, me hoi

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

• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ty) OR (sach thue)) hang ((ma hoi) OR (xa hoi)). hieu vien da tac va hanh vi cua vat~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ty) or (sach thue)) hang ((ma hoi) OR (xa hoi)). hieu vien da tac va hanh vi cua vat~".
• Adding a wildcard symbol may retrieve word variants: su ((sach ty) or (sach thue)) hang ((ma hoi) OR (xa hoi)). hieu vien da tac va hanh vi cua vat*.