Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
van hanh » van thanh, ban hanh, van anh
cao luc » bao luc, cao duc, cau luc
hanh ve » hanh vi, hanh va, hanh kem
cao suc » cao su, cao duc
su tien » su kien, su hien, tu tieng
hieu va » lieu va, hieu qua
nang xa » nang x, lang xa, nang ma
vu nang » vuc nang, va nang, vu dang
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)) vu nang xa hoi. hieu va ((cao luc) OR (cao suc)) van hanh ve su tien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) vu nang xa hoi. hieu va ((cao luc) OR (cao suc)) van hanh ve su tien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (toc sach)) vu nang xa hoi. hieu va ((cao luc) OR (cao suc)) van hanh ve su tien".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) vu nang xa hoi. hieu va ((cao luc) OR (cao suc)) van hanh ve su tien*.