Fatal Error

I am using Global news theme. The home page is working fine. the other pages are not fetching the corresponding post.

As well as the side bar is showing the bellow error:

Fatal error: Call to undefined function related_posts() in /home/chennapa/public_html/wp-content/themes/globalnews/sidebar.php on line 47

Here is the link to the page:

http://bit.ly/S89KZ8

Can anyone help me out to solve this problem.

Thank You