Perhaps you should try some spelling variations:
thu sach » thuat sach, thuoc sach, thu hoach
dua tren » dung tren
van hanh » van thanh, ban hanh, van anh
duc van » duc va, duc tan, duc manh
cam duc » cam xuc, cao duc, pham duc
hieu ve » hieu va, hieu van
cuu tre » cua tre, cau tren, cau treo
tang xa » trang xa, tang ma, lang xa
ky tang » ky nang, ky dang, kho tang
tu sach » su sach, te sach, tu cach
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) OR (tu sach)) ky tang 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) OR (tu sach)) ky tang 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) OR (tu sach)) ky tang xa hoi. hieu ve cam duc van hanh vi ((dua tren) or (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: ((thu sach) OR (tu sach)) ky tang xa hoi. hieu ve cam duc van hanh vi ((dua tren) or (cuu tre))*.