Perhaps you should try some spelling variations:
thien van » thi van
hieu van » hieu va, lieu va, hieu ve
van hanh » van thanh, ban hanh, van anh
xuc van » duc van, luc van, vuc van
nam xuc » cam xuc, nam xua, nam thuc
tu sach » thu sach, su sach, te sach
tang ma » mang may, tang van
ky tang » ky nang, ky dang, kho tang
vu sach » vu bach, su sach, vu khach
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, ma hoa
vi cua » vai cua, di cua

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) or (vu sach)) ky tang ma hoi. ((hieu van) OR (thien van)) nam xuc van hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (vu sach)) ky tang ma hoi. ((hieu van) OR (thien van)) nam xuc van hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (vu sach)) ky tang ma hoi. ((hieu van) OR (thien van)) nam xuc van hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (vu sach)) ky tang ma hoi. ((hieu van) OR (thien van)) nam xuc van hanh vi cua tre*.