Perhaps you should try some spelling variations:
vien dai » hien dai
hanh vai » hanh vi, hanh va, hanh tai
tu sach » thu sach, su sach, te sach
vai cua » dai cua, hai cua, lai cua
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
mai hoi » mai khoi, dai hoi, lai hoi
ky sang » ky dang, ky tang, duy sang
ve cac » va cac, vien cac
tuc va » thuc va, truc va, tuc xa

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