Perhaps you should try some spelling variations:
mai khoi » mai khoa, tai khoa, cac khoi
hanh tai » thanh tai, hang tai, han tai
tu sach » thu sach, su sach, te sach
tai cua » thai cua, tai cuc, tri cua
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach y, sach ty
ky sang » ky nang, ky dang, ky tang
ve cac » va cac, vien cac
ve cam » ve cham, va cam, ve cai

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 sang ((mai khoi) or (xa hoi)). hieu ((ve cam) or (ve cac)) duc va hanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky sang ((mai khoi) OR (xa hoi)). hieu ((ve cam) OR (ve cac)) duc va hanh tai cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ky sang ((mai khoi) or (xa hoi)). hieu ((ve cam) or (ve cac)) duc va hanh tai cua tre*.