Perhaps you should try some spelling variations:
dang duc » dang quoc, dao duc, dang su
hanh vai » hanh vi, hanh tai, hanh van
hieu van » thien van, lieu va, hieu ve
vu sach » vu bach, su sach, vu khach
hanh va » hang va, hanh vi
duc van » duc va, duc tan, duc manh
sach ty » sach y, sach tu, sach thu
hieu va » lieu va, hieu qua
nang ma » tang ma, sang ma, nang cao
ty nang » ky nang, ty xang, ty hang
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: vu sach ty nang ma hoi. ((hieu van) or (hieu va)) dang duc van ((hanh vai) or (hanh va)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach ty nang ma hoi. ((hieu van) OR (hieu va)) dang duc van ((hanh vai) OR (hanh va)) cua tre.
• Adding a wildcard symbol may retrieve word variants: vu sach ty nang ma hoi. ((hieu van) or (hieu va)) dang duc van ((hanh vai) or (hanh va)) cua tre*.