function get_gr(map_ref)
  {
  landr_ref = map_ref.substr(0,2)
  i = 0
  var mapping=new Array("SV","01","02","03","04","05","06","NL","NF","NA","SW","SR","SM","13","14","NW","NR","NM","NG","NB","SX","SS","SN","SH","SC","NX","NS","NN","NH","NC","SY","ST","SO","SJ","SD","NY","NT","NO","NJ","ND","SZ","SU","SP","SK","SE","NZ","NU","47","NK","49","TV","TQ","TL","TF","TA","OV","56","57","58","59","60","TR","TM","TG","64","65")
  while (mapping[i] != landr_ref){i++}
    document.write("<a href='http://www.multimap.com/p/browse.cgi?pc=&GridE=" + Math.floor(i/10) + map_ref.substr(2,3) + "00&GridN=" + i%10 + map_ref.substr(5,3) + "00&scale=25000&title=&cat=h'>" + map_ref + "<\/a>")
  }