Perhaps you should try some spelling variations:
hang dien » quang dien, dang dieu, nhan dien
toc sach » hoc sach, doc sach, thuoc sach
hieu cua » hieu qua, dieu cua, bieu cua
tu sach » thu sach, su sach, te sach
hang di » hang doi, hang vi, hang dich
cac duc » cac du, cao duc, cac dac
duc van » duc va, duc tan, duc manh
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: ((tu sach) or (toc sach)) ky nang x hoi. hieu cua cac duc van ((hang di) OR (hang dien)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (toc sach)) ky nang x hoi. hieu cua cac duc van ((hang di) OR (hang dien)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (toc sach)) ky nang x hoi. hieu cua cac duc van ((hang di) OR (hang dien)) cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (toc sach)) ky nang x hoi. hieu cua cac duc van ((hang di) OR (hang dien)) cua tre*.