Perhaps you should try some spelling variations:
ngoc ngoc » ngo ngoc, loc ngoc
dieu tra » dieu tri, kiem tra, dieu cua
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
va ngoc » van ngoc, vu ngoc, ma ngoc
tra tre » tran tren, tran tri, tran tro
va dan » ca dan, va dau, va dap
va dao » ca dao

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

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