Perhaps you should try some spelling variations:
sach nuoc » sach duoc, cac nuoc, bach tuoc
cau treo » cau theo, cau tren, cau triet
hanh tai » thanh tai, hang tai, han tai
cua tre » cua te, cuu tre, cua triet
va hanh » van hanh, va thanh, va danh
sach ky » sac ky, sach ty, sach kem
hieu va » lieu va, hieu qua
va sach » van sach, va cach, a sach
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: tu ((sach ky) OR (sach y)) nang x hoi. hieu va sach nuoc va hanh tai ((cua tre) or (cau treo))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sach y)) nang x hoi. hieu va sach nuoc va hanh tai ((cua tre) OR (cau treo)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) OR (sach y)) nang x hoi. hieu va sach nuoc va hanh tai ((cua tre) or (cau treo))".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) OR (sach y)) nang x hoi. hieu va sach nuoc va hanh tai ((cua tre) or (cau treo))*.