Perhaps you should try some spelling variations:
dua tren » dung tren
van hanh » van thanh, ban hanh, van anh
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
cao duc » dao duc, cao suc, giao duc
cu tren » tu tren
cac duc » cac du, cac dac, cac nuoc
hieu va » lieu va, hieu qua
tang xa » trang xa, tang ma, lang xa
ky tang » ky nang, ky dang, kho tang

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 tang xa hoi. hieu va ((cac duc) OR (cao duc)) van hanh vi ((dua tren) or (cu tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky tang xa hoi. hieu va ((cac duc) OR (cao duc)) van hanh vi ((dua tren) OR (cu tren))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky tang xa hoi. hieu va ((cac duc) OR (cao duc)) van hanh vi ((dua tren) or (cu tren))*".