Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
ky tang » ky nang, kho tang, ky trong
ky dang » ky nang, ky danh
hieu va » lieu va, hieu qua
va hanh » van hanh, va thanh, va danh
tai cua » thai cua, tri cua, dai cua
va cam » va cham, va cac, va cao
cam tu » cam thu, nam tu, dam tu

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 tang) OR (ky dang)) xa hoi. hieu va cam tu va hanh ((tai cua) OR (tai cuc)) tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ky tang) or (ky dang)) xa hoi. hieu va cam tu va hanh ((tai cua) OR (tai cuc)) tre~".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ky tang) or (ky dang)) xa hoi. hieu va cam tu va hanh ((tai cua) OR (tai cuc)) tre*.