Perhaps you should try some spelling variations:
te sach » toc sach
dinh va » dinh van, dinh ve, tinh va
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
ky dang » ky nang, ky danh
ky lang » ky nang, ky tang, tay lang
tuc va » thuc va, truc va, tuc xa
va cua » va chua, via cua, ca cua
va nam » van nam, ha nam, va nay

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ((ky lang) or (ky dang)) xa hoi. hieu va nam ((duc va) or (tuc va)) dinh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ((ky lang) OR (ky dang)) xa hoi. hieu va nam ((duc va) OR (tuc va)) dinh va cua tre.
• Adding a wildcard symbol may retrieve word variants: te sach ((ky lang) or (ky dang)) xa hoi. hieu va nam ((duc va) or (tuc va)) dinh va cua tre*.