Perhaps you should try some spelling variations:
sach thu » sach thue, sach thieu, sach tham
hieu van » hieu va, thien van, lieu va
sach ty » sach y, sach tu, xach tay
cac xuc » cam xuc, cac nuoc, chat xuc
van cac » van hac, van cau, van bac
cua tre » cua te, cuu tre, cua triet
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
xuc ca » xuc cam, xuc cua
ca dan » cac dan, ca dao
dan vi » doan vi, don vi, dan va
vi cua » vai cua, di cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: so ((sach ty) OR (sach thu)) ((nang xa) or (nang ma)) hoi. hieu van cac xuc ca dan vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so ((sach ty) OR (sach thu)) ((nang xa) OR (nang ma)) hoi. hieu van cac xuc ca dan vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so ((sach ty) OR (sach thu)) ((nang xa) or (nang ma)) hoi. hieu van cac xuc ca dan vi cua tre".
• Adding a wildcard symbol may retrieve word variants: so ((sach ty) OR (sach thu)) ((nang xa) or (nang ma)) hoi. hieu van cac xuc ca dan vi cua tre*.