BusinessLogicPlugin.php

<?php
namespace Craft;

class BusinessLogicPlugin extends BasePlugin
{
        public function getName()
        {
                return 'Business Logic';
        }

        public function getVersion()
        {
                return '1.0';
        }

        public function getDeveloper()
        {
                return 'Admin';
        }
        
        public function getDeveloperUrl()
        {
                return 'https://example.com';
        }

        public function modifyEntrySources(&$sources, $context)
        {
                $newSources = array(
                        array('heading' => 'Post Formats'),
                        array(
                                'label' => 'Articles',
                                'criteria' => array('section' => 'blog', 'type' => 'article')
                        ),
                        array(
                                'label' => 'Links',
                                'criteria' => array('section' => 'blog', 'type' => 'link')
                        )
                );

                $sources = array_merge($sources, $newSources);
        }
}

Create this file in craft/plugins/businesslogic/