Perhaps you should try some spelling variations:
sach nuoc » sach duoc, bach tuoc, dich nuoc
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
hanh hai » thanh hai, nhanh hai, hang hai
su sach » so sach, vu sach
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, x ho

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

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