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quicktags_specialquotes

// Add Quicktags
function custom_quicktags() {

	if ( wp_script_is( 'quicktags' ) ) {
	?>
	<script type="text/javascript">
	QTags.addButton( 'special_quote', 'quote', '<blockquote class="special-quote">', '</blockquote>', 'b', 'Special Quote', 1 );
	</script>
	<?php
	}

}

// Hook into the 'admin_print_footer_scripts' action
add_action( 'admin_print_footer_scripts', 'custom_quicktags' );