Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
vai cua » dai cua, hai cua, lai cua
dan vai » dan va, dan tai, dan vat
cam tuc » cam xuc, nam thuc, dam thuc
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu va, hieu van
ky dang » ky nang, ky danh
ky lang » ky nang, ky tang, tay lang
cam tu » cam thu, nam tu, dam tu
va dan » ca dan, va dao, va dau

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