Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
van dinh » van minh, van dich, xuan dinh
duc cuu » duc suu
va dinh » va kinh, va tinh, vu dinh
cac luc » cau luc, coc luc, cac nuoc
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
cuu tre » cua tre, cau tren, cau treo

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc sach ky ((nang xa) OR (nang ma)) hoi. hieu va cac luc ((va dinh) or (van dinh)) duc cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ky ((nang xa) OR (nang ma)) hoi. hieu va cac luc ((va dinh) OR (van dinh)) duc cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach ky ((nang xa) OR (nang ma)) hoi. hieu va cac luc ((va dinh) or (van dinh)) duc cuu tre".
• Adding a wildcard symbol may retrieve word variants: doc sach ky ((nang xa) OR (nang ma)) hoi. hieu va cac luc ((va dinh) or (van dinh)) duc cuu tre*.