Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
thu sach » tu sach, thuat sach, thu hoach
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
vanh dai » vanh tai, lanh dao, van dao
ty nang » ky nang, ty xang, ty hang
qua cac » cua cac
van dai » van dao, van hai, can dai
cua tre » cua te, cuu tre, cua triet
x hoi » xa hoi, o hoi, x ho

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 nang x hoi. hieu qua cac nuoc va ((van dai) OR (vanh dai)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((thu sach) OR (thuoc sach)) ty nang x hoi. hieu qua cac nuoc va ((van dai) OR (vanh dai)) cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((thu sach) or (thuoc sach)) ty nang x hoi. hieu qua cac nuoc va ((van dai) OR (vanh dai)) cua tre*".