Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu cua » hieu qua, dieu cua, bieu cua
va dinh » van dinh, va kinh, vu dinh
va tinh » may tinh
so viet » hoc viet
nang ma » tang ma, sang ma, nang cao
cua dam » cua dan, cua dai, cua tam
dam tu » nam tu, cam tu, tam tu
y nang » ky nang, ly nang, v nang
ma hoi » mai hoi, xa hoi, ma hoa

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 y nang ma hoi. hieu cua dam tu ((va dinh) or (va tinh)) ve ((su viet) OR (so viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach y nang ma hoi. hieu cua dam tu ((va dinh) OR (va tinh)) ve ((su viet) OR (so viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach y nang ma hoi. hieu cua dam tu ((va dinh) or (va tinh)) ve ((su viet) OR (so viet))".
• Adding a wildcard symbol may retrieve word variants: toc sach y nang ma hoi. hieu cua dam tu ((va dinh) or (va tinh)) ve ((su viet) OR (so viet))*.