Open your own Twitter app from my app using IBAction

I want to implement the natvie Twitter app in my iOS app. I have already done this using Facebook using URL schemes. But I could not find such a thing for Twitter.

On Facebook, I used:

-(IBAction)facebook:(id)sender {
       [[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"fb://"]];
}

But when I try to use

@"Twitter" or @"twitter" or @"tw"

Nothing happens. It would be great if you guys could help me. I did not find anything in Interweb: / If there is something like this, please :)

Thanks in advance:)