Perhaps you should try some spelling variations:
hanh hai » thanh hai, nhanh hai, hang hai
kho tang » cao tang
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
hai cua » thai cua, dai cua, hoi cua
va hanh » van hanh, va thanh, va danh
cam tuc » cam xuc, cam tu, nam thuc
van cam » van nam, van lam, van cau
mai hoi » mai khoi, dai hoi, lai hoi
ky tang » ky nang, ky dang, ky trong
cua tre » cua te, cuu tre, cua triet
ma hoi » xa hoi, ma hoa, me hoi
tuc va » thuc va, truc va, tuc xa

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) OR (kho tang)) ((ma hoi) or (mai hoi)). hieu van cam tuc va hanh hai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky tang) OR (kho tang)) ((ma hoi) OR (mai hoi)). hieu van cam tuc va hanh hai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ky tang) OR (kho tang)) ((ma hoi) or (mai hoi)). hieu van cam tuc va hanh hai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ky tang) OR (kho tang)) ((ma hoi) or (mai hoi)). hieu van cam tuc va hanh hai cua tre*.