Perhaps you should try some spelling variations:
dieu tra » dieu tri, kiem tra, dieu cua
loc ngoc » lo ngoc, ngoc ngoc, le ngoc
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
tra tre » tran tren, tran tri, tran tro
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
va dan » ca dan, va dao, va dau
va loc » van loc, va doc, va loi

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) OR (nang ma)) hoi. lieu va loc ngoc ((va dan) OR (cac dan)) dieu tra tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((nang xa) OR (nang ma)) hoi. lieu va loc ngoc ((va dan) or (cac dan)) dieu tra tre~".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang xa) OR (nang ma)) hoi. lieu va loc ngoc ((va dan) or (cac dan)) dieu tra tre*.