Perhaps you should try some spelling variations:
ban hanh » ban hang
cham hoc » cham soc, chat hoc, cham hoi
sang mai » sang ma, sang tai, lang mai
tu sach » thu sach, su sach, te sach
hoc ban » hoc bang, hoc dan, hoc bai
hieu va » lieu va, hieu qua
hieu vu » hieu ve, hieu su, dieu vu
mai hoi » mai khoi, dai hoi, lai hoi
ky sang » ky nang, ky dang, ky tang
tu can » tu ban, tu cac, thu canh
vi cua » vai cua, di cua
cua te » cua tu

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (tu can)) ky sang mai hoi. ((hieu vu) OR (hieu va)) cham hoc ban hanh vi cua te~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (tu can)) ky sang mai hoi. ((hieu vu) OR (hieu va)) cham hoc ban hanh vi cua te~".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (tu can)) ky sang mai hoi. ((hieu vu) OR (hieu va)) cham hoc ban hanh vi cua te*.