avevo risolto così, va bene uguale?
Codice PHP:
<?
$query27="SELECT a1.cognome_admin AS cognome_admin_1, a2.cognome_admin AS cognome_admin_2
FROM a_admin a1, a_admin a2, protocollo_attivita pa1
WHERE pa1.referente_1=a1.id_admin AND pa1.referente_2=a2.id_admin
ORDER BY cognome_admin_1 ASC";
$ris_query27=mysql_query($query27, $conn);
while($row27=mysql_fetch_array($ris_query27)){?>
<?=$row27['cognome_admin_1']?> e <?=$row27['cognome_admin_2']?>