Add Hatom data markup from microformats.org

Google webmaster tools returns 3 errors at structured data section.

The theme lacks from entry-title, author and updated hatom-feed data.

I’ve managed to resolve this error with this code on my child theme functions.php

// Fixing rich snippets for hatom-feed at hatom-entry
	//add hatom data
function add_hatom_data($content) {
    $t = get_the_modified_time('F jS, Y');
    $author = get_the_author();
    $title = get_the_title();
if (is_singular()) {
        $content .= '<div class="hatom-extra" style="display:none;visibility:hidden;"><span class="entry-title">'.$title.'</span> was last modified: <span class="updated"> '.$t.'</span> by <span class="author vcard"><span class="fn">'.$author.'</span></span></div>';
    }
    return $content;
    }
add_filter('the_content', 'add_hatom_data');

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