Perhaps you should try some spelling variations:
trinh doc » trinh do, trinh hoa, trinh co
va trinh » van trinh, va tinh, lap trinh
cu tren » tu tren, dua tren
va cham » va chat, va tham
dai hoi » dai hoc, dai hai, dai moi
mai hoi » mai khoi, lai hoi, mai doi
ky tang » ky nang, ky dang, kho tang
san ky » sang ky, van ky, dan ky
va cam » va cac, va cao, va cai
doc cu » doc cua, doc cuoc
tu san » thu san, tu ban, tu can

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 san ky tang ((mai hoi) OR (dai hoi)). hieu ((va cam) OR (va cham)) duc va trinh doc cu tren~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu san ky tang ((mai hoi) OR (dai hoi)). hieu ((va cam) or (va cham)) duc va trinh doc cu tren~".
• Adding a wildcard symbol may retrieve word variants: tu san ky tang ((mai hoi) OR (dai hoi)). hieu ((va cam) or (va cham)) duc va trinh doc cu tren*.