Perhaps you should try some spelling variations:
thu sach » thuat sach, thuoc sach, thu hoach
van hanh » van thanh, ban hanh, van anh
hieu van » hieu va, thien van, lieu va
kho tang » cao tang
hanh di » hanh vi, hanh de, hang di
duc van » duc va, duc tan, duc manh
hau duc » huu duc, ha duc, pham duc
van hau » van ha, van hai, van dau
ky tang » ky nang, ky dang, ky trong
tu sach » su sach, te sach, tu cach
cua tre » cua te, cuu tre, cua triet
di cua » dai cua, doi cua, de cua

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((thu sach) or (tu sach)) ((ky tang) OR (kho tang)) xa hoi. hieu van hau duc van hanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((thu sach) OR (tu sach)) ((ky tang) OR (kho tang)) xa hoi. hieu van hau duc van hanh di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((thu sach) or (tu sach)) ((ky tang) OR (kho tang)) xa hoi. hieu van hau duc van hanh di cua tre".
• Adding a wildcard symbol may retrieve word variants: ((thu sach) or (tu sach)) ((ky tang) OR (kho tang)) xa hoi. hieu van hau duc van hanh di cua tre*.