shortcodes.php

 /**
 * Post Authors Post Link Shortcode
 *
 * @author Bill Erickson
 * @link http://www.billerickson.net/wordpress-post-multiple-authors/
 * 
 * @param array $atts
 * @return string $authors
 */
function be_post_authors_post_link_shortcode( $atts ) {

	$atts = shortcode_atts( array( 
		'between'      => null,
		'between_last' => null,
		'before'       => null,
		'after'        => null
	), $atts );

	$authors = function_exists( 'coauthors_posts_links' ) ? coauthors_posts_links( $atts['between'], $atts['between_last'], $atts['before'], $atts['after'], false ) : $atts['before'] . get_author_posts_url() . $atts['after'];
	return $authors;
}
add_shortcode( 'post_authors_post_link', 'be_post_authors_post_link_shortcode' );