Perhaps you should try some spelling variations:
cach thuc » anh thuc
hanh hai » thanh hai, nhanh hai, hang hai
van hanh » van thanh, ban hanh, van anh
su sach » so sach, vu sach
hai cua » thai cua, dai cua, hoi cua
cac thu » cac thoi
hieu va » lieu va, hieu qua
mai hoi » mai khoi, dai hoi, lai hoi
ky sang » ky dang, ky tang, duy sang
cua tre » cua te, cuu tre, cua triet

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