Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
van hanh » van thanh, ban hanh, van anh
dua tren » dung tren
ky tang » ky dang, kho tang, ky trong
hieu ve » hieu va, hieu van
cam duc » cam xuc, cao duc, pham duc
duc van » duc va, duc tan, duc manh
cuu tre » cua tre, cau tren, cau treo
ve cam » ve cham, ve cac, va cam

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