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

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 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 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 van hanh vi ((dua tren) or (cuu tre))*.