Perhaps you should try some spelling variations:
hanh vai » hanh va, hanh tai, hanh van
su sach » so sach, vu sach
cac tuc » cac toc, cac tu, cac tac
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu va, hieu van
mai hoi » mai khoi, dai hoi, lai hoi
ky sang » ky dang, ky tang, duy sang
tuc va » thuc va, truc va, tuc xa
ve cac » va cac, vien cac

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 ve cac tuc va ((hanh vai) OR (hanh vi)) 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 ve cac tuc va ((hanh vai) OR (hanh vi)) 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 ve cac tuc va ((hanh vai) OR (hanh vi)) cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ((ky sang) or (ky nang)) mai hoi. hieu ve cac tuc va ((hanh vai) OR (hanh vi)) cua tre*.