Perhaps you should try some spelling variations:
sach nuoc » sach duoc, cac nuoc, bach tuoc
hanh hai » thanh hai, nhanh hai, hang hai
vu sach » vu bach, su sach, vu khach
sach ky » sac ky, sach y, sach ty
hieu va » lieu va
va hanh » van hanh, va thanh, va danh
hai cua » thai cua, dai cua, hoi cua
cua tre » cua te, cuu tre, cua triet
x hoi » xa hoi, o hoi, 5 hoi

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 ky nang ((x hoi) OR (x ho)). ((hieu va) or (hieu qua)) sach nuoc va hanh hai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach ky nang ((x hoi) OR (x ho)). ((hieu va) OR (hieu qua)) sach nuoc va hanh hai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu sach ky nang ((x hoi) OR (x ho)). ((hieu va) or (hieu qua)) sach nuoc va hanh hai cua tre".
• Adding a wildcard symbol may retrieve word variants: vu sach ky nang ((x hoi) OR (x ho)). ((hieu va) or (hieu qua)) sach nuoc va hanh hai cua tre*.