Perhaps you should try some spelling variations:
van thanh » ban thanh, van tuan
thanh va » thanh van, hanh va, thanh ha
dua tren » dung tren
su sach » so sach, vu sach
ky tang » ky dang, kho tang, ky trong
hieu va » lieu va, hieu qua
cac duc » cac du, cao duc, cac dac
duc van » duc va, duc tan, duc manh
cu tren » tu tren

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