Add strings to a two-dimensional array
<p>How do I add objects to a two-dimensional array? The array is initiated with a couple items (see below), but I need to add more items to the array.</p>

<pre><code>      images_ = [[NSArray alloc] initWithObjects:
             [NSArray arrayWithObjects:@"http://farm3.static.flickr.com/2735/4430131154_95212b8e88_o.jpg", @"http://farm3.static.flickr.com/2735/4430131154_17d8a02b8c_s.jpg", nil],
             [NSArray arrayWithObjects:@"http://farm5.static.flickr.com/4001/4439826859_19ba9a6cfa_o.jpg", @"http://farm5.static.flickr.com/4001/4439826859_4215c01a16_s.jpg", nil],nil];
</code></pre>
