Perhaps you should try some spelling variations:
su sach » so sach, vu sach
sach ty » sach y, sach tu, sach thu
hieu va » lieu va, hieu qua
cao luc » bao luc, cao duc, cao suc
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
va cao » va cac, va co, va dao
luc va » duc va, tuc va, loc 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: su sach ty ((mang may) or (nang x)) hoi. hieu va cao luc va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty ((mang may) OR (nang x)) hoi. hieu va cao luc va hanh vi cua tre.
• Adding a wildcard symbol may retrieve word variants: su sach ty ((mang may) or (nang x)) hoi. hieu va cao luc va hanh vi cua tre*.