Change text on back button in iPhone SDK [solved]

Question

I'm using iPhone SDK 3.1.3 and I tried look like that

self.navigationItem.backBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"Back" style:UIBarButtonItemStylePlain target:nil action:nil];

It's not working and nothing effect. So, I tired

self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"Back" style:UIBarButtonItemStylePlain target:nil action:nil];

button text it change and stye it squre. I click it and it's not go to back.

I want to change back button to text @"Back". How to write it ?

I also read in there but not work for me.