Perhaps you should try some spelling variations:
hieu hien » bieu hien, chieu chien, dieu khien
bich ngoc » bich nga, dinh ngoc
dieu hien » dieu khien, dieu kien, bieu hien
so sach » so sanh, bo sach, co sach
ngoc ca » ngoc ha, ngoc chau, ngoc canh
sach ky » sac ky, sach y, sach ty
di cua » dai cua, doi cua, de cua
dan di » danh di, dan da, dan de
ca dan » cac dan, ca dao
cua tu » cua tuc, cua su, cua cu
o hoi » co hoi, o hoc, o hai
x hoi » xa hoi, x ho, 5 hoi

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ky nang ((x hoi) or (o hoi)). ((hieu hien) OR (dieu hien)) bich ngoc ca dan di cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky nang ((x hoi) OR (o hoi)). ((hieu hien) OR (dieu hien)) bich ngoc ca dan di cua tu*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ky nang ((x hoi) or (o hoi)). ((hieu hien) OR (dieu hien)) bich ngoc ca dan di cua tu*".