Perhaps you should try some spelling variations:
hanh thai » nhanh thai, hinh thai, hanh tai
hieu van » hieu va, thien van, lieu va
thai cua » than cua, tai cuc, tri cua
duc manh » suc manh, duc anh, duc minh
quoc ban » quoc bao, quoc lan, quoc quan
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va
tang ho » tang cho, tung ho, tang ha
ky tang » ky nang, ky dang, kho tang
cua tre » cua te, cuu tre, cua triet
ho hai » hoc hai, pho hai, cho hai

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 ky tang ho hai. ((hieu ve) or (hieu van)) cac ((quoc ban) or (duc manh)) hanh thai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky tang ho hai. ((hieu ve) OR (hieu van)) cac ((quoc ban) OR (duc manh)) hanh thai cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ky tang ho hai. ((hieu ve) or (hieu van)) cac ((quoc ban) or (duc manh)) hanh thai cua tre*.