Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
va kinh » va tinh, qua kinh
va dinh » van dinh, va tinh, vu dinh
sach ly » sach y, sach lo, sach ty
hieu va » lieu va, hieu qua
nang ma » tang ma, nang cao, mang may
sang ma » tang ma, sang tao, mang may
su viet » so viet
va dao » ca dao
dao tu » dao tuc, dao tru, tao tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ly ((nang ma) OR (sang ma)) hoi. hieu va dao tu ((va dinh) or (va kinh)) va su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ly ((nang ma) OR (sang ma)) hoi. hieu va dao tu ((va dinh) OR (va kinh)) va su viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ly ((nang ma) OR (sang ma)) hoi. hieu va dao tu ((va dinh) or (va kinh)) va su viet".
• Adding a wildcard symbol may retrieve word variants: toc sach ly ((nang ma) OR (sang ma)) hoi. hieu va dao tu ((va dinh) or (va kinh)) va su viet*.