Perhaps you should try some spelling variations:
thanh dai » thanh hai, thanh tai, thanh dat
nang mai » nang ma, nang tai, lang mai
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
mai hoi » mai khoi, dai hoi, lai hoi
hieu va » lieu va
cua tre » cua te, cuu tre, cua triet
xuc va » tuc va, luc va, xac va

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky nang mai hoi. ((hieu va) or (hieu qua)) cam ((xuc va) OR (duc va)) thanh dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang mai hoi. ((hieu va) OR (hieu qua)) cam ((xuc va) OR (duc va)) thanh dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang mai hoi. ((hieu va) or (hieu qua)) cam ((xuc va) OR (duc va)) thanh dai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang mai hoi. ((hieu va) or (hieu qua)) cam ((xuc va) OR (duc va)) thanh dai cua tre*.