Access of possible undefined property text through a reference with static type class

programming flash
1

button.addEventListener(MouseEvent.CLICK, produce);

function produce(Event:MouseEvent):void
{
var t1:String=text1.text;
var t2:String=text2.text;
result.text = t1.text + “-” + t2.text;
}

But the same error keeps showing up, related to the var t1 and var t2 lines:
Access of possible undefined property text through a reference with static type class

What should I do? I already tried removing the String indication,
trade : by =,
including import flash.events.Event in the begining

but nothing seems to work… HELP

Thank you in advance,

Andrea