function check(elementID)
{ 
    document.getElementById(elementID).checked = 1;
}

function unknown_year()
{
  if (document.getElementsByName("year_unknown")[0].checked) {
      document.getElementsByName("year_b")[0].value = "0000";
      document.getElementsByName("year_b")[0].disabled = true;      
  }
  else {  		
      document.getElementsByName("year_b")[0].value = "";
      document.getElementsByName("year_b")[0].disabled = false;
      document.getElementsByName("year_b")[0].focus();
  };   
}

function unknown_year_death()
{
  if (document.getElementsByName("year_d_unknown")[0].checked) {
      document.getElementsByName("year")[0].value = "0000";
      document.getElementsByName("year")[0].disabled = true;
  }
  else {
      document.getElementsByName("year")[0].value = "";
      document.getElementsByName("year")[0].disabled = false;
      document.getElementsByName("year")[0].focus();
  };   
}