public function message($recipients, $subject, $body, $copy_self = FALSE) {
    /**
     * Clean up the passed data per these rules:
     * 
     * 1) Message must be sent to at least one recipient
     * 2) No HTML permitted
     */
    if(!empty($subject) && is_string($subject)) {
      $subject = trim(strip_tags(stripslashes($subject)));
    } else {
      throw new LinkedInException('LinkedIn->message(): bad data passed, $subject must be of type string.');
    }
    if(!empty($body) && is_string($body)) {
      $body = trim(strip_tags(stripslashes($body)));
    } else {
      throw new LinkedInException('LinkedIn->message(): bad data passed, $body must be of type string.');
    }
    if(!is_array($recipients) || count($recipients) < 1) {
      // no recipients, and/or bad data
      throw new LinkedInException('LinkedIn->message(): at least one message recipient required.');
    }
    
    // construct the xml data
		$data   = '<?xml version="1.0" encoding="UTF-8"?>
		           <mailbox-item>
		             <recipients>';
    $data  .=     ($copy_self) ? '<recipient><person path="/people/~"/></recipient>' : '';
                  for($i = 0; $i < count($recipients); $i++) {
                    if(is_string($recipients[$i])) {
                      $data .= '<recipient><person path="/people/' . trim($recipients[$i]) . '"/></recipient>';
                    } else {
                      throw new LinkedInException ('LinkedIn->message(): bad data passed, $recipients must be an array of type string.');
                    }
                  }
    $data  .= '  </recipients>
                 <subject>' . htmlspecialchars($subject) . '</subject>
                 <body>' . htmlspecialchars($body) . '</body>
               </mailbox-item>';
    
    // send request
    $query    = self::_URL_API . '/v1/people/~/mailbox';
    $response = $this->fetch('POST', $query, $data);
		
		/**
	   * Check for successful request (a 201 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */ 
    return $this->checkResponse(201, $response);
	}