Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu ve » hieu va, hieu van
ve luat » va luat, ve thuat
nang xa » nang x, lang xa, nang ma
su tien » su kien, su hien, tu tieng
tuc va » thuc va, truc va, duc va
dao ve » bao ve, dap ve, dau ve
ve su » va su

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((te sach) OR (toc sach)) ky nang xa hoi. hieu ve luat ((tuc va) or (tuc xa)) dao ve su tien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ky nang xa hoi. hieu ve luat ((tuc va) OR (tuc xa)) dao ve su tien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) OR (toc sach)) ky nang xa hoi. hieu ve luat ((tuc va) or (tuc xa)) dao ve su tien".
• Adding a wildcard symbol may retrieve word variants: ((te sach) OR (toc sach)) ky nang xa hoi. hieu ve luat ((tuc va) or (tuc xa)) dao ve su tien*.