function input_paid()
 {
     $r = '';
     $r .= '<div id="payment"> ';
     $r .= '<h2> ' . _('Payé par') . ' </h2>';
     $mp = new Acc_Payment($this->db);
     $mp->set_parameter('ledger_source', $this->id);
     $r .= $mp->select();
     $r .= '</div>';
     return $r;
 }