Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
hieu va » lieu va, hieu qua
cac tac » cac toc, cac tai, cac tap
cac dac » cac dan, cac dai, cac dang
cac bac » cac bai, cac ban, cac cach
van dau » van dao, phan dau
dau cua » dai cua, day cua, cau cua
cua tre » cua te, cuu tre, cua triet

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 xa hoi. hieu va ((((cac tac) OR (cac dac))) or (cac bac)) va van dau cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang xa hoi. hieu va ((((cac tac) OR (cac dac))) OR (cac bac)) va van dau cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang xa hoi. hieu va ((((cac tac) OR (cac dac))) or (cac bac)) va van dau cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang xa hoi. hieu va ((((cac tac) OR (cac dac))) or (cac bac)) va van dau cua tre*.