Perhaps you should try some spelling variations:
dua tren » dung tren
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
cao duc » dao duc, cao suc, giao duc
cuu tre » cua tre, cau tren, cau treo
cam duc » cam xuc, pham duc, nam duoc
hieu va » lieu va, hieu qua
tang xa » trang xa, tang ma, lang xa
ty tang » tay tang, ty xang, ty hang

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