Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
hanh vai » hanh vi, hanh tai, hanh van
hanh va » hang va, hanh vi
duc van » duc va, duc tan, duc manh
cau duc » cao duc, cau luc, chu duc
van cau » van dau, van hau, van chat
sach ty » sach tu, sach thu, xach tay
nang ma » tang ma, sang ma, nang cao
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, ma hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu ((sach ty) or (sach y)) nang ma hoi. hieu van cau duc van ((hanh vai) or (hanh va)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ty) OR (sach y)) nang ma hoi. hieu van cau duc van ((hanh vai) OR (hanh va)) cua tre.
• Adding a wildcard symbol may retrieve word variants: tu ((sach ty) or (sach y)) nang ma hoi. hieu van cau duc van ((hanh vai) or (hanh va)) cua tre*.