Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu cua » hieu qua, dieu cua, bieu cua
nuoc van » nuoc va, nuoc san, luoc van
van hanh » van thanh, ban hanh, van anh
nang xa » nang x, lang xa, nang ma
cua dat » cua vat, cua dan, cua dai
hanh di » hanh vi, hanh de, hang di
cua tre » cua te, cua triet, dua tren
cuu tre » cau tren, cau treo
y nang » ky nang, ly nang, v nang

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 xa hoi. hieu cua dat nuoc van hanh di ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach y nang xa hoi. hieu cua dat nuoc van hanh di ((cua tre) OR (cuu tre)).
• Adding a wildcard symbol may retrieve word variants: toc sach y nang xa hoi. hieu cua dat nuoc van hanh di ((cua tre) or (cuu tre))*.