Perhaps you should try some spelling variations:
van thanh » ban thanh, van tuan
hieu van » hieu va, thien van, lieu va
van hanh » ban hanh, van anh, van ban
tu sach » thu sach, su sach, te sach
ky lang » ky nang, ky dang, tay lang
ky tang » ky nang, ky dang, kho tang
cua tre » cua te, cuu tre, cua triet
vi cua » vai cua, di cua

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 lang) OR (ky tang)) xa hoi. hieu van nam cua ((van hanh) or (van thanh)) vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky lang) OR (ky tang)) xa hoi. hieu van nam cua ((van hanh) OR (van thanh)) vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ky lang) OR (ky tang)) xa hoi. hieu van nam cua ((van hanh) or (van thanh)) vi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ky lang) OR (ky tang)) xa hoi. hieu van nam cua ((van hanh) or (van thanh)) vi cua tre*.