Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
va tuong » va thong, xa truong, va phuong
nang xa » nang x, lang xa, nang ma
hieu va » lieu va, hieu qua
cua tre » cua te, cua triet, dua tren
cuu tre » cau tren, cau treo
sach v » sach va, sach y, sach 2
v nang » va nang, vu nang, van nang
cac tu » cac thu, cach tu, cac du

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 v nang xa hoi. hieu va cac tu ((va tuong) or (va thuong)) doi ((cua tre) OR (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach v nang xa hoi. hieu va cac tu ((va tuong) OR (va thuong)) doi ((cua tre) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach v nang xa hoi. hieu va cac tu ((va tuong) or (va thuong)) doi ((cua tre) OR (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: toc sach v nang xa hoi. hieu va cac tu ((va tuong) or (va thuong)) doi ((cua tre) OR (cuu tre))*.