** FILE ** The Pittsburgh Steelers defense react as Minnesota Vikings' quarterback Fran Tarkenton (10) recovers his own fumble in the end zone for a safety in second quarter of Super Bowl IX in New Orleans at Tulane Stadium, in this Jan. 12, 1975 photo. Identifiable players are Steelers' Ernie Holmes (63), Joe Greene (75), and Mike Wagner (23). The Steelers won 16-6. They remain the only NFL team to win four Super Bowls in six years, yet what might separate the Steel Curtain Steelers of the 1970s from other NFL champions is what they did off the football field. (AP Photo/Charlie Kelly)