Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
thu sach » tu sach, thuat sach, thu hoach
van hanh » van thanh, ban hanh, van anh
truc van » truc va, thuc van, truc ban
dao truc » dao tuc, dao tru, dai truc
hanh va » hang va, hanh vi
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va
xang xa » lang xa, mang xa, ang xa
va cua » va chua, via cua, ca cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((thu sach) OR (thuoc sach)) ty xang xa hoi. ((hieu va) or (hieu qua)) dao truc van hanh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((thu sach) OR (thuoc sach)) ty xang xa hoi. ((hieu va) OR (hieu qua)) dao truc van hanh va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((thu sach) OR (thuoc sach)) ty xang xa hoi. ((hieu va) or (hieu qua)) dao truc van hanh va cua tre".
• Adding a wildcard symbol may retrieve word variants: ((thu sach) OR (thuoc sach)) ty xang xa hoi. ((hieu va) or (hieu qua)) dao truc van hanh va cua tre*.