Perhaps you should try some spelling variations:
hieu sau » hieu su, hieu suat, tieu su
viet cua » viec cua, viet qua, biet cua
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
hieu va » lieu va, hieu qua
soc van » hoc van, oc van, sac van
van anh » van thanh, tuan anh, van minh
viet ca » viet ha, viet co, viet a

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: tu sach ky nang xa hoi. ((hieu va) OR (hieu sau)) cham soc van anh ((viet cua) OR (viet ca)) viet~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang xa hoi. ((hieu va) or (hieu sau)) cham soc van anh ((viet cua) OR (viet ca)) viet~".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang xa hoi. ((hieu va) or (hieu sau)) cham soc van anh ((viet cua) OR (viet ca)) viet*.