Perhaps you should try some spelling variations:
thu sach » thuat sach, thuoc sach, thu hoach
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van anh
hanh di » hanh vi, hanh de, hang di
cao duc » dao duc, cao suc, giao duc
cau duc » cau luc, chu duc, cau truc
tang xa » trang xa, tang ma, lang xa
ky tang » ky nang, ky dang, kho tang
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 xa hoi. hieu van ((cau duc) OR (cao 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 xa hoi. hieu van ((cau duc) OR (cao 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 xa hoi. hieu van ((cau duc) OR (cao duc)) van hanh di cua tre".
• Adding a wildcard symbol may retrieve word variants: ((thu sach) or (tu sach)) ky tang xa hoi. hieu van ((cau duc) OR (cao duc)) van hanh di cua tre*.