Perhaps you should try some spelling variations:
vanh dai » van dai, vanh tai, lanh dao
mai khoi » mai khoa, tai khoa, cac khoi
tu sach » thu sach, su sach, te sach
dai cuu » dai cua, dai huu
cuu tre » cua tre, cau tren, cau treo
hieu ve » hieu va, hieu van
tuc va » thuc va, truc va, duc va
v nang » va nang, vu nang, van nang
ve cam » ve cham, ve cac, va cam

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) or (v nang)) mai khoi. hieu ve cam ((tuc va) OR (tuc xa)) vanh dai cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky nang) OR (v nang)) mai khoi. hieu ve cam ((tuc va) OR (tuc xa)) vanh dai cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ky nang) or (v nang)) mai khoi. hieu ve cam ((tuc va) OR (tuc xa)) vanh dai cuu tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ky nang) or (v nang)) mai khoi. hieu ve cam ((tuc va) OR (tuc xa)) vanh dai cuu tre*.