The sisters enjoyed a resurgence in the 1950s when they were booked at the FlamingoHotel in Las Vegas, which led to television appearances and more recording.
Since the 1940s when the FlamingoHotel first opened with a splash, the strip has consistently been an international attraction, more resorts popping up with each decade.
Johnston also told fans at the city's FlamingoHotel that securing manager Walter Smith's future, along with assistant Ally McCoist and first-team coach Kenny McDowall, for another year offered the club continuity.